Tsumego(2) : Answer

Here is the answer for Tsumego (2).

The answer is P2.



After the exchange from 2-5, white can't play at "A", since it is a self atari. Since white's group has no eye and it can't play at "A" (which is the key point of killing black's group), white is dead.

There is also an idea to play P1. Though it also leads black to live, but it is not the best choice, since the result is only seki.



Again, N1 is the key point which can't be occupied by either player, since it will be a self atari.