Question

    When the world was very young, people lived in hot places. They 1. live in cold places because they could not keep warm there.

At first men didn't know 2. to make a fire. Sometimes trees were hit by lightning. Then a fire was started. A fire was very important for three reasons. It kept them warm. Wild animals were frightened when they saw it. And when food 3. cooked on the fire, it tasted much better.

But men didn't know how to make a fire. When they had a fire, they didn't let it stop burning. If it went 4., they had to wait for lightning to start another fire. Sometimes they had to wait for years.

Later, they learned how to make a fire. But it was not easy 5. make something burn.

Now we have matches. We can carry them in our pockets and make a fire whenever we want it.

Answer

1.didn't

2.how

3.was

4.out

5.to

【解析】

【主旨大意】本文是一篇说明文。文章讲述了在原始社会的时候，人们选择生活在温暖的地方，因为他们________懂如何取暖。一开始只能靠雷电取火到后来他们学会了生火，但是点燃一些东西仍然是不容易的。而现在我们有了火柴，只要我们有需要，随时都可以生火。

1.句意：他们不住在寒冷的地方，因为他们不能在那里保暖。根据前句中的“people lived in hot places.”可知此处表示人们不住在冷的地方，本句讲的是过去的事情，所以时态用一般过去时，故填didn't。

2.句意：起初人们不知道________生火。根据句意可知此处表示“怎样做某事”，应用how to do表达。故填how。

3.句意：当食物在火上烹调时，味道就好多了。根据句意可知，此处表示“被烹调”，应用被动语态，主语是单三人称，时态是过去时。故填was。

4.句意：如果它熄灭了，他们就得等闪电再引起一场火。根据句意可知，此处表示“熄灭”。go out“熄灭”，是固定搭配。故填out。

5.句意：但要让东西燃烧起来并不容易。本句考查固定句型It is ＋adj.＋to do sth.表示“做某事是……的”。故填to。