I'm reading Beginning Go, by Peter Shotwell and Susan Long. Chapter 8 problem 2 says that Black is to show how to kill a group of White's choosing, White's turn. Killing the top right group is easy, but how can B kill the bottom W group if W plays at A?

I tried with B extending to H4, then white hane at H5 - can't figure out a B win there. I also tried with B hane to D2, still couldn't figure out a win for B. It seems like if W plays at A (E4), that W group is pretty set. (Game's still a loss for W.)

I spent an embarrassing amount of time on this, so I'm hoping I just am misunderstanding the question and it really means "Black to show how to a group of BLACK's choosing after White plays".

I think that the point is that White to play chooses which group to save.

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Oh that makes more sense, although I couldn't figure out any way for white to save the top group. Am I correct that B can't take bottom W after wE4?

This turned out to be more complicated than I thought. Here is what I came up with. Your move at 'A' saves the bottom group if white plays correctly and, if black insists, can even cost him the game. White can choose to save the top if he wishes, but either way black kills the other group and white loses.

Black should not try to kill the group white helps. He can win without it and you shouldn't strive to kill groups or complicate the game when you can win in a simpler way. When you are losing then yes, complicate stuff and try to get your opponent to make a mistake or miss something, but when you are winning keep it simple.

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"You have to walk before you can run. Black 1 was a walking move.
I blushed inwardly to recall the ignorant thoughts that had gone through
my mind before, when I had not realized the true worth of Black 1."
-Kageyama Toshiro on proper moves

In other words.. White can easily save one group, then Black will kill the other.

You need to be able to see how to kill each group, if White chooses to save the other.

Wow, what a great analysis. I'm amazed and delighted by the complexity in a supposed "beginner" problem. I hadn't even tried to use W to threaten B's top group - I kept it very local when trying to solve the problems. How cool to have W strike back!

Thank you for explaining it. I really love Go. I feel I've learned a lot in two weeks, but there's a universe more to know.

I'm sure there's elderly professional 9dans who would say something like "I feel I've learned a lot in six decades, but there's a universe more to know."

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