请从A、B、C、D四个选项中选出可以填入空白处的最佳选项。
1. Leifeng is _______ helpful person who always helps others when they are in trouble.
A. an B. a C. / D. the
2. —Do you know when the 30th Olympic Games will be held in London?
—Yes. _______ July 27th, 2012.
A. In B. At C. On D. For
3. .— Is that boy with a pair of sunglasses Jim?
—That _ _____ be Jim. He has gone to Beijing.
A. mustn't B. needn't C. shouldn't D. can't
4. —Can you visit grandfather tomorrow?
