和 情态动词can, must,may ,will,would等等连用时,用be动词原形比如,He may be right 他可能是对的
跟在情态动词后面时用BE。
1.动词不定式后面如:I want to be a doctor.2.情态动词后,如:can,may,could,shall.should.3祈使句中:Don't be late.Be careful.
有些词是后面要加动词原形,如must may ....,不用变am is are