It’s + adj.+ (of / for) sb to do sth.譯作“(某人)做某事是…的”.It 是形式主語,不定式結(jié)構(gòu)是真正主語.of / for后面的sb是不定式的邏輯主語.
1.當(dāng)形容詞是可修飾人的形容詞,即sb和adj.有主系表關(guān)系時,sb前用of.如 It’s clever of you to answer the question so quickly./ It’s kind of you to help me a lot.這樣的形容詞有：kind,nice,rude,clever,silly,foolish等.
2.當(dāng)形容詞是不可以修飾人的形容詞,即sb和adj.沒有主系表關(guān)系時,sb前用for.如 It’s easy for her to clean the window by herself./ It’s important for us to learn English well.這樣的形容詞有：easy,hard,difficult,important,necessary,dangerous等.