1. Early next morning, she heard planes passing overhead and wondered how she could send a signal.
    第二天清晨，她听到头上有飞机飞过，却不知道怎样才能发出信号，

2. Early next morning, she heard planes passing overhead and wondered how she could send a signal.
    第二天一大早，她听到头顶上有飞机飞过，但不知道怎样才能发个信号。

3. Every year the United States is host to an average of 78,000 foreign high school level students, of which 3,000 are Brazilian.
    美国平均每年要接待78,000名中学学历程度的外国学生，其中3,000个来自巴西。

4. But we are the ones who signal to businesses that what they are doing is okay — every time we buy their products.
    每当我们购买他们的产品时，我们就在向企业发出信号，告诉他们可以这样做。

5. Was it the signal?
    这是那信号吗?

6. We finally stopped in front of a narrow street lined on either side with small one-level houses.
    我们终于在一条狭窄的、两边都排列着矮小平房的街道前面停了下来。

7. While active, child-bearing age women are most likely to have low iron stores, he notes, "Men are not safe, especially if they don't eat meat and have a high level of physical activity."
    他还指出，虽然积极锻炼的育龄妇女最有可能铁离子储量低，"但男性也并非不缺铁，尤其是在他们不吃肉类而又从事高强度的体力活动的情况下。"

8. The soldiers lay in ambush, waiting for the signal to open fire.
    士兵布下伏兵，等待开火的信号。

9. The city at one time must have been prosperous, for It enjoyed a high level of civilization.
    这座古城在一个时期准是很繁荣的,因为它曾享有高度文明.

10. The cellar is below road level.
    地窖在路面以下。