Question

5．他與疾病作頑強(qiáng)斗爭(zhēng)很勇敢．
It is braveof him to fightagainst the disease．

Answer 1

分析 of him to fight．

解答 答案：of him to fight．結(jié)合句意是表達(dá)某人做某事是怎樣的用句型It's+adj+of sb+to do sth，與…斗爭(zhēng)結(jié)合against用fight against，故答案是of him to fight．

點(diǎn)評(píng) It's+adj．+for sb．+to do（ sth．） 與 It's+adj．+of sb．+to do（ sth．）的區(qū)別
用of 的話，adj就用來(lái)形容sb的．即形容詞是描述不定式行為者的性格、品質(zhì)的，如kind，good，nice，right，wrong，clever，careless，polite，foolish等，用of sb..故可以換成 sb is adj to do 
比如：it‘s nice of you to help me．=you are nice to help me．
1 It's very kind of you to help me．你能幫我，真好．
2 It's clever of you to work out the maths problem．你真聰明，解出了這道數(shù)學(xué)題．
用for 是因?yàn)榍懊娴腶dj是來(lái)描述do后面的sth．即形容詞僅僅是描述事物，不是對(duì)不定式行為者的品格進(jìn)行評(píng)價(jià)，用for sb．，這類形容詞有difficult，easy，hard，important，dangerous，（im）possible等．如 
1 It's very dangerous for children to cross the busy street．
對(duì)孩子們來(lái)說(shuō)，穿過(guò)繁忙的街道很危險(xiǎn)．