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The question is difficult to be answered. （误）

The question is difficult to answer. （正）

The question is difficult for sb. to answer. （正）

The question is too difficult to answer. （正）

The question is too difficult for sb. to answer. （正）

The question is too difficult to be answered. （正）

The question is too difficult to be answered by sb. （正）

【注】

1. 现代语法把“形容词+ 不定式”整个部分，看作 is 的表语（补足语），不再细分。

2. 不定式用主动形式时，相当于省却了逻辑主语for sb.

3. 形容词之前有了程度副词too 修饰时，不定式表示结果。此时，用主动形式或被动形式均可。

    在一种特殊结构中，有些形容词可以与动词不定式连用，此时，句子的主语实际上是动词不定式的宾语。这样的形容词有 easy, hard, difficult, impossible, good, ready 以及 enough 之前和 too 之后的形容词。

    He's easy to please.(= To please him is easy. 或 It is easy to please him.)讨好他很容易。

    Japanese is difficult for Europeans to learn. (= It is difficult for Europeans to learn Japanese.)对欧洲人来说，学日语很难。

    （以上内容摘自《牛津英语用法指南》第三版284.4）

    James doesn't speak very clearly. It is difficult to understand him. (= James doesn't speak very clearly. He is difficult to understand. )

(摘自英国 Raymond Murphy 著的英语在用：《剑桥中级英语语法》第四版中文版 P.130)

    所以，不能说：The question is difficult to be answered.可以说：The question is difficult to answer. / It is difficult to answer the question./ To answer the question is difficult.

有没有The question is difficult to be answered?

解答如下：

没有以上那种表达结构，以上句子表达是错误的。

(1)The question is difficult to be answered.（错误）

(2)The question is difficult to answer（正确）

(3)The question is difficult for me to answer（正确）

(4)To answer the question is difficult （正确）

(5)It is difficult to answer the question （正确）

(6)It is difficult for me to answer the question （正确）