单选题
阅读下面短文，从短文后所给的[A]、[B]、[C]三个选项中选出能填人相应空白处的最佳选项。
Issac Newton was{{U}} (41) {{/U}}great English Scientist (科学家),{{U}} (42) {{/U}}when he was thinking hard about his work, he often forgot{{U}} (43) {{/U}}things. One morning Newton got up early. He began{{U}} (44) {{/U}}at once. He worked on a very difficult problem. He was still thinking about it hard when it was time{{U}} (45) {{/U}}breakfast. Mary brought a pan of water and an egg to his room. But Newton wanted to stay by{{U}} (46) {{/U}}and said to Mary, "You can put the egg on the table. I'll boil (沸腾，煮) it myself." Mary put the egg beside Newton's watch on the table and said, "You must boil the egg{{U}} (47) {{/U}}four minutes and then it will be ready." Then she went out of the room. But when she went into the room again an hour{{U}} (48) {{/U}}, she saw him{{U}} (49) {{/U}}by the pan, and having the egg in his hand. He had put the watch in the pan and was boiling it. But he didn't know{{U}} (50) {{/U}}he was doing.
【正确答案】 A
【答案解析】由于great的第一个音节是辅音发音，所以用a。
【正确答案】 C
【答案解析】前句说牛顿是伟大的科学家，后面又说他会忘记做某事，所以前后句间应该是转折关系。选[C]but。
【正确答案】 A
【答案解析】这里没有特指另外某件事，所以用[A]other而不是[C]another。
【正确答案】 A
【答案解析】习惯用法：begin to do sth．
【正确答案】 C
【答案解析】it is time for breakfast。早餐的时间到了。
【正确答案】 A
【答案解析】stay by himself，独自一个人呆会。
【正确答案】 A
【答案解析】三个选项中只有for才能接表示一段时间的four minutes。
【正确答案】 B
【答案解析】习惯用法：an hour later一小时后。
【正确答案】 C
【答案解析】see有两种用法,see sb. doing sth．看见某人正在做某事；see sb. do sth.，看见某人做了某事，后者强调过程。三个选项中只有 C符合see的用法。
【正确答案】 A
【答案解析】But he didn't know what he was doing。但是他并不知道他自己正在做什么。