【正确答案】with
【答案解析】译文：当看到小丑的时候，孩子们突然爆发出咯咯的笑声。explode with是固定搭配，“爆发、突发”。答案为with.
4.He tried to use his own weight to push the attacker off but he was _____________ balance. [答疑编号506430020528：针对该题提问]
【正确答案】off
【答案解析】译文：他试图用自己的重量把进攻者推走，但是他失去平衡了。off balance是固定搭配，意思是“失去平衡”。答案为off.
5.I used to stay ___________________ late with my mom and watch movies. [答疑编号506430020529：针对该题提问]
【正确答案】up
【答案解析】译文：我曾经和我妈妈一起熬夜看电影。stay up 是固定词语搭配，意思是“熬夜”。答案为up.
6.The discovery of the new drug is________________ great significance for people. [答疑编号506430020530：针对该题提问]
【正确答案】of
【答案解析】译文：新药品的发现对人类有重大意义。be of + n.结构相当于形容词的作用，因此横线处填of，意思是“有重大意义的”。答案为of.
IV
Section A
Directions: The following sentences are grammatically incorrect or incoherent. Improve them. 1.Sir Humphry Davy was an excellent literary critic as well as being a great scientist. [答疑编号506430020531：针对该题提问]
【正确答案】Sir Humphry Davy was an excellent literary critic as well as a great
scientist.
【答案解析】being 和前面的was使用重复，因此应该删去being。答案为Sir Humphry Davy was an excellent literary critic as well as a great scientist.
2.Roger plays with rabbits but also hunts them. This is one reason why Roger likes rabbits. [答疑编号506430020532：针对该题提问]
【正确答案】Roger plays with rabbits but also hunts them. This is the reason why Roger
likes rabbits.
【答案解析】why引导的从句对前面的先行词起解释作用，因此要用定冠词the。答案为Roger plays with rabbits but also hunts them. This is the reason why Roger likes rabbits.
3.Hanging by their tails from the branches, the children gazed at the monkeys. [答疑编号506430020533：针对该题提问]
【正确答案】The children gazed at the monkeys, whose tails were hung from the branches. 【答案解析】前后两个句子的主语要保持一致，很明显本题两个句子主语分别为monkeys 和 children，可换为以children为主语，以定语从句的形式引出从句。答案为：The children gazed at the monkeys, whose tails were hung from the branches.
4.Last night I had my first taste of sake（日本清酒）. It is a Japanese beverage made from rice. [答疑编号506430020534：针对该题提问]
【正确答案】Last night I had my first taste of sake, which is a Japanese beverage made from rice.
【答案解析】which引导的宾语从句，修饰先行词sake，答案为：Last night I had my first taste of sake, which is a Japanese beverage made from rice.
5.John Wayne was the biggest box-office attraction of his time who appeared in over 200 movies. [答疑编号506430020535：针对该题提问]
【正确答案】John Wayne, who appeared in over 200 movies, was the biggest box-office
attraction of his time.
【答案解析】后面的定语从句修饰的先行词应为John Wayne，因此应将其调到主语之后。答案为：John Wayne, who appeared in over 200 movies, was the biggest box-office attraction of his time.
Section B
Directions: Supply a topic sentence for the following paragraph.
______________________________________________. A good starting point is narrowing down the type of car you want or need. Be realistic. You may envision yourself cruising around town in a little convertible, but that won't leave much room for the kids and dogs. Once you've settled on the basic vehicle, do some research to find out which vehicles have good reliability ratings. The Internet and books can help you pick out the high maintenance turkeys. The next step is finding the model you are looking for. Used car lots will give you an idea of price, but they can be expensive and full of used car salesmen. Check your local paper, car buyers' magazines and the Internet. When you finally track down what looks good, arrange to have your mechanic inspect it. Never omit this step. After your mechanic gives the car the OK, all that's left is to haggle over the price. [答疑编号506430020536：针对该题提问]
【正确答案】There are several steps to purchase a suitable car for you.
【答案解析】本题是要求给本段补充首句。由于首句一般是主旨句，因此我们先通读全文看 下本文主要内容，本文主要是介绍了怎么买适合的车。然后从第二句a starting point，第六句的the next step，我们可以具体得出本文讲述的是买到合适的汽车的步骤。