I have no prize for you.

I would guess a), but I'm pretty sure it's not it.

I'd assume it's "d".
Reason being: White has a lot of influence, so according to "Attack and Defense", White should grab some territory to balance things out, and "d" is huge.
The other thing is, "d" is big, but I guess "b" could be called urgent. It prevents Black from stabilizing his left group and putting even more pressure on it, so it could be called Sente. Furthermore it strengthens White's position and develops the corner. On top, it utilize White's thickness, because White can chase Black against the wall.
So, I think this is the better choice in this state of the game.

"b"!

A because for some odd reason, everything is telling me to play calmly at A.

a and c look like 5-7 kyu level moves. destroying the opponents potential. without looking at anything else. blocking an extention from a shimari seems to be somehow hardcoded to 5-7 kyu players (or at least i get that impression) (This better not be one of the correct answers, or I'll feel very very stupid )

e and b look slow and rather passive, giving black every opportunity to choose his preferred strategy.

g looks too aggressive with the cutting-points in the wall and without support from a strong group in the bottom left.

h and i (though quite different moves) look to be on the unimportant side of the board where neither player can develop much (low side of the shimari and p12 already makes sure that black can't build big things there.

j is gote and black gets b16 in sente so the corner is not that big anyway. this looks like a nice early endgame move.

d indeed looks nice, but it leaves a lot of cutting points. the top left thickness only has value towards the left and center if it is strong. If there is weakness in it, black can probably easily neutralize the wall and strengthen the left. That makes me doubt it is a move a pro will play d

f feels very solid. After white f there is nothing from white that black can make use of. It makes the white position super thick and this will allow white to force black into defending (specially on the left). allowing white enough time to build something in the center and come back in time to play on the bottom before black does. therefore I think the pro played at f.

f. Feels like honte.

A, C: Big, but not urgent.

D: Aji-keshi. White replies 'F' or L17.

H, I: Not big, not urgent.

G: Premature. Black can reply with 'B', now white's stone at 'G' is weak, and the cut at C16 starts to become relevant.

J: Small and gote.

B and E: Sente for both sides. If black gets 'E', it is sente to play the double approach, and the whole west side is strengthened.
If white plays 'B', it threatens 'G' next, and the white wall enters the game.

F: A solid move, but IMHO, too slow. It affects no life-and-death issues. It grabs some territory, but there is plenty of room for invasions. Black can tenuki with 'E' and maintain sente.

In conclusion: I'd play 'B'. When black defends, then I'd play 'F'.

I'll go with 'f', though my second choice would be 'a'.

g feels urgent to me, because otherwise, the top white wall can be attacked, making white's thickness worthless.

my gut says b, as that is what i would play...but F seems more stable, so i'll go with that..

I am going with A. F seemed important locally, but I don't think its that urgent. Right now white needs to build more territory rather than worrying about a moyo.

I would play 'e' (or perhaps 'b'), to make miai of 'g' and 'a'.

I think it has to be G, if white plays something else black will defend and white will lose their chance.

D. I thought that this was an interesting choice of move, which is why I selected it.

The sequence that followed in the game was this:

Click Here To Show Diagram Code

[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . 5 . . . . . . . . . . |
$$ | . . . X X . X 6 X 1 . . . . . . . . . |
$$ | . . O X O X 4 3 X O . . . . O O . . . |
$$ | . . . O O O X X O . . . . O . O X . . |
$$ | . . . . . O O O . . . . . . O X X . . |
$$ | . . X . . . . . . . . . . O X . X . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . O . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 2 . . . . . . . . . . . . . . . . |
$$ | . . . 9 . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . O . . . . . 7 . . . . . , . . . |
$$ | . . . . . . . . . . . 8 . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

and white continued to develop the bottom.

I found it particularly interesting how Cho Chikun immediately took advantage of the atari at to help his shape out a bit.

Thanks again to all who participated.

Ok, it's not too hard once you've seen Kirby's diagram, but here's the solution:

Click Here To Show Diagram Code

[go]$$B Black has achieved profit in the 'x' area in sente
$$ ---------------
$$ | . . . . . . .
$$ | . O 2 O X . .
$$ | x 4 1 O X . .
$$ | 3 O O X . X .
$$ | x X X X . . .
$$ | x x . . . . .
$$ | . . . . . . .[/go]

Click Here To Show Diagram Code

[go]$$W If white gets to play 1 first, it no longer works for black
$$ ---------------
$$ | . . . . 1 . .
$$ | . O . O X . .
$$ | . 3 2 O X . .
$$ | . O O X . X .
$$ | . X X X . . .
$$ | . . . . . . .
$$ | . . . . . . .[/go]

Click Here To Show Diagram Code

[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . j X X . X . X d . . . . . . . . . |
$$ | . . O X O X . . X O . . . . O O . . . |
$$ | . . . O O O X X O f . . . O . O X . . |
$$ | . . . . . O O O . . . . . . O X X . . |
$$ | . . X . . . . . . . . . . O X . X . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . g x . . . . . . . . . . O . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . i . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . b . . . . . . . . . . . . . . . . |
$$ | . . e . . . . . . . . . . . . h . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . O . . . . . c . . . . . , . . . |
$$ | . . . . . . . . . a . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

j, d, and f are small and gote and thus out of the question. i feels strangely disconnected to the other white stones; h is probably a bit better, but gives away too much territory. So we are left with: making a shimari, invading directly at g, or extending at a or c. Of these, the invasion at 'g' feels much too direct because black can easily sacrifice one stone and g will be too close to white's thickness.

Out of these, I pick e. I believe it is sente, ie. black has to defend at the point marked x. If he does so, e is clearly in a better position than b because the corner is not so open. After black defends, you make perfect shape at a, and your thickness in the top should help you in all the fighting to come. If black plays a instead, then the invasion at g will become very painful for him. If you play a first, black can approach at b and although I think it is not terrible for white, it feels a bit too easy for black.

I guess a.

edit: ah I see the answer is already posted. Why does black answer 5 in the game? He could still live if white captures there.

If white captures, his wall becomes perfect with no defects. Black must then live in gote, at the same time weakening his group on the left. It's bigger than it looks for white to capture.