do you know where your mather is i

问题描述:

do you know where your mather is i
do you know where your mather is i think he ------on the playground .he likes doingexercise?a---mustrun b---mustberuning c---couldrun d---couldberunning

b.由于是现在进行时而且表示主观,所以是must be谢好评,祝学业有成