be difficult to do的不定式表被動

類似于 be difficult to do 結構中，若主語與其后的不定式為動賓關系，那么該不定式習慣上要用主動形式表示被動意義。如：

She was difficult to understand at times. 有時候她很不容易理解。

能用于此結構的形容詞主要有convenient, dangerous, difficult, easy, hard, impossible, interesting, nice, pleasant, safe, unpleasant 等。這類結構的特點是句子主語必須其后不定式的邏輯賓語。如：

The poem is easy to understand. 這首詩容易理解。

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

He is hard to get along with. 他這個人很難相處。