形容词,副词和介词的用法(要百分百正确的)答:(2)形容词difficult,hard,dangerous,necessary,safe,unsafe, useful,pleasant,possible,impossible,probable等作表语时,主语一般是物或形式主语 it而不是人。 ①He is necessary to do it. (×) ②It is necessary for him to do it. (√) 他很有必要做那件事。 注意表语形容词的用法: ill, well意为“有...