You're right. Sometimes the answer key is wrong. I have to explain this to my professors from time to time, and it's always annoying. And in those cases I ha

You're right. Sometimes the answer key is wrong. I have to explain this to my professors from time to time, and it's always annoying. And in those cases I have paid money to be graded incorrectly. I would be happy if I were you though. The point of this exercise is to learn, and I'll bet you'll remember that water molecule for a long time :-)