I am confused with reduced adverb clauses A TOEFL book says that when there is a connctor 'once', it should be reduced in passive as follows: Once (it is) submitted, your thesis will be reviewed. The sentence above makes sense to me. But my question is that when 'once' is used in active,why can't it be reduced like this: Once you submit your thesis, you will graduate. Once submitting your thesis, you will graduate. Is it just because 'once' is used here?