What should Black do in the following situation?

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[go]$$c What should Black do in this situation?
$$ ---------------------
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . X . . |
$$ | . . . . . . . . . |
$$ | . . . . , . . . . |
$$ | . . . O . . X . . |
$$ | . . , . . . O . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ ---------------------[/go]

Thanks.

I asked Fuego, which is stronger than I am at 9x9 (computers tend to do well on small board sizes).

It recommended this play:

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[go]$$Bcm1 Black Play
$$ ---------------------
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . X . . |
$$ | . . . . . . . . . |
$$ | . . . . , . . . . |
$$ | . . . O . 1 X . . |
$$ | . . , . . . O . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ ---------------------[/go]

If white continues back to connect, black can be happy with a nice wall:

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[go]$$Bcm1 Black has done well
$$ ---------------------
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . X . . |
$$ | . . . . . . . . . |
$$ | . . . 5 , . . . . |
$$ | . . . O 3 1 X . . |
$$ | . . , . 4 2 O . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ ---------------------[/go]

Maybe because of this, its choice for white is to treat the stone lightly:

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[go]$$Bcm1 Black Play
$$ ---------------------
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , 2 . . X . . |
$$ | . . . . . . . . . |
$$ | . . . . , . . . . |
$$ | . . . O . 1 X . . |
$$ | . . , . . . O . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ ---------------------[/go]

I want to ignore, and tenuki @ C6

but I can't say if that's any better or worse.

In the first and second diagram I think the exchange is acceptable to black only because it is a 9x9 board. On a full size board, white is doing much better, running ahead on the 4th line while black's extension is too close to his wall.

I suppose one danger of 9x9 games: you may get some bad instincts when playing moves that work well in 9x9, but not in 19x19.