Caribou are wary animals with excellent hearing, so stalking them over the treeless landscape, getting close enough to kill it with nothing but a handheld lance, as Dorset people did, required exceptional hunting skill.

1. so stalking them over the treeless landscape, getting close enough to kill it
2. so to stalk them over the treeless landscape and get close enough to kill one
3. so in order to stalk them over the treeless landscape and get close enough to kill one
4. and so in order to stalk it over the treeless landscape, getting close enough to kill it
5. and so stalking them over the treeless landscape and getting close enough in order to kill it

问题是，to do可以做主语？后面的required应该是从句的谓语了，那么to stalk是required的动作发出者？

Require除了表示“要求”require sb to do sth,或者sb be required to do sth之外。

Require本身还有“需要”的意思，比如：

The floor requires washing. 这地板该洗了

This job requires a clear head .这份工作需要头脑清晰。

所以，在本题当中的Require就是“需要”的意思。而不是to stalk要求hunting skills;

而是说to stalk “需要”hunting skills.

不知道这么说是不是能理解。

对阿，不定式做主语，没什么奇怪的阿。难道一定是人做主语，MM才觉得不奇怪么？呵呵，我给了两个例子，都不是人做主语阿。

The floor requires washing. 这地板该洗了

This job requires a clear head .这份工作需要头脑清晰。

只不过一般情况下，不定式做主语的时候，我们通常用it的形式主语，比

如：

It is important to learn English. 其实应该是 To learn English is

important.

给几个不定式做主语的例句吧，看看是不是可以帮助理解：

To work with a new machine is not easy job. 使用一台新的机器工作不是

那么容易的。

To make him understand the question takes some time. 让他明白这个道理

还是需要一点时间的。