(2011·山东)He had his camera ready ________ he saw something that would make a good picture.

A good advertisement should ____ the consumers and direct their attention to the product.

I was telling about my exciting travels when he _________ with a story of his own.

Sam ______ some knowledge of the computer just by watching others working on it.

I _________ the boy to work hard at his lessons, but he wouldn’t listen.