[正] It is necessary for you to do so.
注:一個形容詞可以用來指“行為”,又可以用來指“行為者”,如 kind, good, foolish, nice, careful, careless 這類皆是。這種形容詞可以接用 of 來造句,如 It is kind of you. (行為)= You are kind. (行為者)。另外有些形容詞,只能用來指“行為”,不能用來指“行為者”,如 necessary, impossible, inconvenient, unbearable 這類皆是。這種形容詞是不可以接用 of 來造句的,它只能接用 for,例如 It is necessary for you to go. 而不能說 You are necessary to go.