Hi. I have encountered this opening many times. It has to be slightly bad for White. But I have absolutely no idea how I should answer it.

Click Here To Show Diagram Code

[go]$$B
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . 4 . 2 . . |
$$ | . . . . . . . . . |
$$ | . . . . 1 . 3 . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

So what's Black strongest reply?

Well, what's the komi? Komi is so big on a 9x9 that the right answer is very dependent on it.

Well then I would be interested to know the answer for a komi of 7.5 and also the answer for zero komi.

There are many options here. Upper right san-san is a good point since creates a quite likely living group while limiting W territory and doesn't lead to an easy double attack. If W feels like attacking, he'll likely split the two groups and try to kill something anyway. If she doesn't, lower-right san-san or lower 5-3 are good with 7.5 komi, since as a weak rule of thumb, if W has two living groups with large komi, W wins. With no komi, seems really bad, and is probably best to switch to the lower-left san-san to create some potential chaos.

_________________
Geek of all trades, master of none: the motto for my blog mostlymaths.net

Click Here To Show Diagram Code

[go]$$Bc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . a . . . . . |
$$ | . . , . 4 . 2 . . |
$$ | . . 5 . . . . . . |
$$ | . . . . 1 . 3 . . |
$$ | . . . . . . . . . |
$$ | . . , b c . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

My first thought was , aiming at "a". If White replies on the top, then "b" or "c".

Click Here To Show Diagram Code

[go]$$Bc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . 4 . 2 . . |
$$ | . . . . . . . . . |
$$ | . . . . 1 . 3 . . |
$$ | . . . . . . . . . |
$$ | . . , 5 . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

Here is another thought. Maybe a bit passive, but it stakes out a large corner in the bottom right. Because it is a territory grabber, it may be a good no-komi play.

_________________
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At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

I thoght about your first 5, but usually if I play like this it turns out I start a passive game and komi kills me. So, same direction, one further

_________________
Geek of all trades, master of none: the motto for my blog mostlymaths.net

I thought about the first variation here, but felt it might leave white too much scope on the bottom left. My other initial considerations were:

Click Here To Show Diagram Code

[go]$$Bc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , b 4 . 2 . . |
$$ | . . . . . . . . . |
$$ | . . a . 1 . 3 . . |
$$ | . . . . . . . . . |
$$ | . . , . c . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

A makes miai of a sort. White will have to start another group so you can hope to use the thickness to fight and build territory in the other two corners. B is a contacty fighting move aiming to mix things up immediately. C is similar to Bill's suggestion. I'm not sure if it's more or less passive, though.