is所用的范畴是单词单数形式,而且时态为一般现在时或者现在进行时的时候.
EG：Is she a student?
Is she doing her homework?
are所用的范畴时单词复数形式,而且时态为一般现在时或者现在进行时的时候.
EG：Are they students?
Are they doing their homework?
do所用的范畴是第二人称和单词的复数形式,而且时态为一般现在时的时候
EG：Do you want to go to the zoo?
Do they enjoy the party?
can所用的范畴为征询某人意见或建议时,没有单词单复数的影响
EG:Can I have the cake?