Is this a seki or Black wins?

[zagory]

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If White plays at L3 or C1, Black will kill him and then Black can make eyes(White plays at C3 and Black responses with D3). But if White pass, Black needs to put two stones at L3 and C1 to completely surround White and than White plays at C3 and Black can't make eyes. So is this a seki or is this a Black win? Can black pass and say "White stones inside are dead"?

[Li Kao]

It's a seki.
Whichever player first moves at C1 or E3 dies.
What's important is the shape that's created if w moves first. The L shape is an eyeshape that lives unless it's in the corner, so B lives if W moves first.

[zagory]

thx, I thought it was a seki.

[Joaz Banbeck]

Can black pass and say "White stones inside are dead"?

He can, but white's reply will be:"Prove it. Show me how you can kill them." Whereupon if black tries to kill them, he dies.

[Li Kao]

The problem with proving is that you need to do it using hypothetical play if you're using territory scoring, and at least the kgs client doesn't support that.

[dfan]

Yet another reason I prefer area scoring (at least when explaining the game to beginners).