1. … be made to work for us?: ……能用来为我们工作吗？
be made to 为make 的被动语态形式。主动形式时"make"一词后跟不带"to"的不定式作宾补，但转化为被动语态则必须加"to"，如：

The boss makes him repair the car.
He is made to repair the car.

2. … do a number of simple jobs that are now done by human beings: …… 做当今人类做的许多简单工作。
a number of "许多"修饰可数名词，如:
A number of them are girls.
that 一词引导定语从句修饰 simple jobs.

3. as we know: 正所周知
as 一词引导非限制从句，功能类似which, 既可放在主句前也可放在主句后，而which 带起的非限制从句只能放在主句后 (见本课point 7)。如：

Mark Twin is a famous writer, as we know.
As we know, it is Bell who invented the telephone.

4. … give warning by making a lot of noise: 通过产生声音来报警。
"by" 一词为介词，后跟动名词，表示通过什么方式或手段做某事。如：
He improves his English by speaking aloud every day.

5. It may be possible to train animals to work in factories.: 在工厂训练动物做工也许成为一种可能。
"It be + adjective + to V" 句式中"it"为形式主语, 不定式为真正主语。如：
It is important to study English in modern times.

6. … pigeons, which are birds with good eyesight… : ……鸽子是具有很好视力的一种鸟……
which 一词引导的为非限制性定语从句。如：
This pin, which my brother gave me, is made of gold.

7. … are being used to watch out…: ……正用来密切注意……
are being used 为现在进行时的被动语态，表示此时此刻正在被做。如：
The apples are being picked.

8. It takes three to five weeks to train a pigeon to do this.: 训练一只鸽子做此事需三到五周。
"It takes somebody 时间 to do something "此句型意为"做某事需什么人多少时间"。如：
It takes me an hour to go to school.