题目

阅读理解Every person has hisbirthday. People in different countries spend their birthdays in different ways.Here are four people from different countries. They are talking about how theyusually spend their birthdays in their countries. Jack comes from Spain. Mytwenty-first birthday is on a Saturday , he says. I'm going outwith my friends. To wish me a happy birthday, they will pull on my eartwenty-one times, once for each year. It's an old habit. Some people pull onthe ear just once, but my friends are very strict! Mr. Sato is from Japan. He'sgoing to be sixty tomorrow. In my country, pe . ___ to nuclear radiation, even for a short time may produce variants（变异体）of genes in human bodies.   A. Being exposed     B. Having exposed    C. Exposed          D. After being exposed