用it作形式主语的用法改写下列各个句子
【小题1】To learn something about the use of “it” is necessary.
________________________________________________________________________
【小题2】Crying over spilt milk is no use.
________________________________________________________________________
【小题3】That the boss was behaving pretty strangely struck me.
________________________________________________________________________
【小题4】Whether you come or not doesn’t interest  me.
________________________________________________________________________
【小题5】Tom is believed to win the race.
________________________________________________________________________