Confused about Learn-to-play-go 5.36 Ko #6

Can someone please help me understand Learn-to-play-go 5.36 #6?

The accepted answer is to play at A6, and I see that it results in a Ko situation, but I don’t understand how that is advantageous. It seems like black would respond with B6, threatening the potential eye at C5. I don’t see how white would get out of that situation.

What am I missing?