—Where is Jack?I can’t find him anywhere.
—He__________ his homework upstairs.
A.might have done
B.must have done
C.must be doing
D.must do
C
must be doing是对目前正在发生的事进行推测。
—Where is Jack?I can’t find him anywhere.
—He__________ his homework upstairs.
A.might have done
B.must have done
C.must be doing
D.must do
C
must be doing是对目前正在发生的事进行推测。