be easy (difficult)后接不定式要用主動表被動

對于某些“be+形容詞+to do”結構，當其中的不定式與句子為被動關系時，不定式習慣上要用主動形式表示被動意義。這類形容詞以easy和difficult為代表，主要包括awkward, convenient, dangerous, difficult, easy, hard, impossible, interesting, nice, pleasant, safe, tough, tricky, unpleasant 等。如：

The sentence is easy to translate. 這個句子很容易翻譯。

The work is difficult to do. 這項工作很難做。

The river is dangerous to swim in. 在這河里游泳很危險。

Your writing is impossible to read. 你的書寫沒法認。

Do you think the water is safe to drink? 你認為這水喝起來安全嗎?

Volleyball is very interesting to watch. 打排球看起來很有意思。

A man so difficult to please must be hard to work with. 一個如此難以取悅的人一定不好共事。

A foreign language isn’t by any means (=is by no means) easy to master. 要精通外語絕對不是件簡單的事。

His style may be simple, but it is pleasant to read. 他的風格雖然單一，但讀起來仍令人愉快。

有少數用于類似結構的形容詞(如fit, ready, free等)，其中的不定式用主動式和被動式均可。如(www.hz123456.com)：

The water is not fit to drink [to be drunk]. 這水不適合飲用。

The letters are ready to post [to be posted]. 這信已準備好可以寄了。