二、单项选择。
1. What is a telephone used _____, class?
A. to B. in C. for D. about
2. Was a car invented _____ March 4, 1876?
A. on B. in C. at D. of
3. Can you tell me _____ the train was invented?
A. what B. who C. when D. which
4. I think the _____ invention is a mobile phone. What about you?
A. helpful B. more helpful C. helpfulest D. most helpful
