1. have no idea

不知道；不清楚

eg. However, I have no idea where to go.

但是，我拿不定主意去哪儿。

eg. Right now, we have no idea of the impact of these drug residues or what we can do about them.

目前，我们还不知道这些药物残留会对身体产生什么影响，也不知道该对它们做些什么。

2. ahead of

在…之前

eg. Let's cut through the woods and get ahead of them.

咱们穿过树林抄近路赶到他们前面去。

eg. He had to work hard to remain ahead of his classmates.

他必须努力学习以保持他在同学中的领先地位。

3. run out of

用完

eg. We ran out of coal,and had to burn wood.

我们的煤用光了，只好烧柴。

eg. As long as the atmosphere has molecules of hydrogen and molecules of oxygen, why should we ever run out of water?

既然大气中存在着大量的氧分子和氢分子，那为什么还会出现水资源短缺的问题？