Charles Darwin, a young man just out of university, knew perfect well that he had to depend on _____ when he set out on a voyage of discovery around the world. 

Understanding the cultural habits of another nation,especially ______containing as many different subcultures as the United States,is a complex task.

Did Lisa tell you      in the letter？

 — I don’t know whether I should go abroad or not, Mum.— I leave _______ to your own judgment whether you should do it.

This watch looks nice. I'd like to buy _______, too.