Michael Redmond states in his book ( p 142 ) that the circled black move is sente against the corner.

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[go]$$Bc
$$ --------------+
$$ . . . . . X . |
$$ . . B . X O . |
$$ . . . . . O . |
$$ . O X X W . . |
$$ . . . . O . . |
$$ . . X X O . . |
$$ . . X O . O . |
$$ . . X O . X . |
$$ . . . X . . . |[/go]

So my problem is: What can B do in the corner? Any help?

As a side issue:

Well, white's next move from the book offers a hint. How about this for an anti-tsumego:

White to live.

Click Here To Show Diagram Code

[go]$$Bc
$$ --------------+
$$ . . . . . X . |
$$ . . X . X O . |
$$ . . . . . O . |
$$ . O X X O . . |
$$ . . . . O X . |
$$ . . X X O . . |
$$ . . X O . O . |
$$ . . X O . X . |
$$ . . . X . . . |[/go]

_________________
Patience, grasshopper.

You are fast I tried that:

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[go]$$Bc seki?
$$ --------------+
$$ . . . . . X . |
$$ . . X 7 X O 2 |
$$ . . . . 6 O . |
$$ . O X X O 5 3 |
$$ . . . . O 1 8 |
$$ . . X X O . 4 |
$$ . . X O . O . |
$$ . . X O . X . |
$$ . . . X . . . |[/go]

Here, Black could get a ko by playing 7 at 8 and then answering White 7 with Q19.

But, what about Black 3 at a?

_________________
Patience, grasshopper.

OK, I surrender to your beautiful move, let me steal it.
So I tried:

Click Here To Show Diagram Code

[go]$$Wc
$$ --------------+
$$ . . . . . X . |
$$ . . X 2 X O 5 |
$$ . . . . 1 O . |
$$ . O X X O . 6 |
$$ . . . . O X . |
$$ . . X X O . 7 |
$$ . . X . 8 O . |
$$ . . X . 0 X 3 |
$$ . . . X 4 9 . |
$$ . . . B . a . |
$$ . . . . b c . |
$$ . . . . . d . |
$$ . . . . . . . |[/go]

Wa,Bb,Wc,Bd won't produce another w eye nor escape, so w dies. But plenty of aji in the lower right, though!

edit: oops I forgot the circled black stone, so there is less aji. B4 at 10 might be better shape now.