When I was 19，I had got a job in my local bookstore. Living in the large city，I usually saw many strange customers(顾客)，most of  1  were teenagers. They didn’t come often；I forgot all the customers  2  two. One night a 15-year-old girl came in looking for a book with a boy. They seemed to find what they wanted to buy. But  3  they came to the counter（柜台），the girl found she was a dollar or two short to buy the book，and she took

4 all her money to prove it. She looked so disappointed. Just then I remembered my discount card and 5  was still active，so I told the girl   6  to worry. I put in my code（密码），being happy that I could help them with this card. With the book in her hand she gave me  7   thankful smile，and then she and the boy got out of the store happily，leaving me feeling content，too.  8 fact, sometimes a little thing can also make one’s world beautiful.

如果用³H、¹⁵N、³²P、³⁵S标记噬菌体后，让其侵染细菌，在产生的子代噬菌体的组成结构成分中，能够找到的放射性元素（）

A.外壳中可找到¹⁵N和³⁵S、³H

B.DNA中可找到³H、¹⁵N、³²P

C.外壳中可找到¹⁵N和³⁵S

D.DNA中可找到¹⁵N、³²P、³⁵S