请看下面的句子，答案是哪个？原因是什么？
He is __________ to win the match.
A. possible B. difficult C. sure D. easy
此题应选C。其余几项不能选为答案，是因为它们在通常情况下，easy, difficulty, possible, impossible, necessary 等形容词后接不定式时，通常不以人作主语。请再看实例：
他可能会赢得这场比赛。
误：He is possible to win the match.
正：It is possible for him to win the match.
我很难按时完成它。
误：I’m difficult to finish it in time.
正：It’s difficult for me to finish it in time.
他可以轻而易举地把它干好。
误：He’s easy to do it well.
正：It’s easy for him to do it well.
他不可能成功。
误：He is impossible to succeed.
正：It is impossible for him to succeed.
他有必要买台电脑。
误：He is necessary to buy a computer.
正：It is necessary for him to buy a computer.
对于以上结构，有些形容词有时也可用人作主语，但要注意，此时这个主语必须是其后不定式的逻辑宾语。如：
他很容易(难)相处。
正：He’s easy (difficult) to get along with.
正：It’s easy (difficult) to get along with him.