As luck would have it, he was caught by the teacher again.

不幸的是，他又一次被老师逮个正着。

She held the little boy by the right hand.

她抓着小男孩的右手。（这里用“by”与用“with”意思区别很大。）

Are you there?

等于句型：Do you follow me?

If you think he is a good man, think again.

如果你认为他是好人，那你就大错特错了。

If my mother had known of it she'd have died a second time.

要是我妈妈知道了，她会从棺材里爬起来。

That took his breath away.

他大惊失色。（很形象的说法啊~）

Rubber easily gives way to pressure.

橡胶很容易变形。

The elevator girl reads between passengers.

开电梯的姑娘在没有乘客时看书。

between=without，相同用法：

She modeled between roles. 她不演戏时去客串下模特。

Students are still arriving.

学生还没有到齐。

I must not stay here and do nothing.

我不能什么都不做待在这儿。

They went away as wise as they came.

他们一无所获。（这句有点意料之外，不过仔细一想貌似的确有道理啊~）

I won't do it to save my life.

我死也不会做。

Nonsense, I don't think his painting is any better than yours.

胡说，我认为他的画比你好不到哪去。（好吧……原来是说两个人画得都不咋样……）

Traditionally, Italian presidents have been seen and not heard.

从传统上看，意大利总统有名无权。

Work once and work twice.

一次得手，再次不愁。

You don't want to do that.

你不应该去做。

My grandfather is nearly 90 and in his second childhood.

我祖父快90岁了，什么事都需要别人来做。