What would you do if it ______ tomorrow ?—We have to carry it on , since we’ve got everything ready .

In April，thousands of holidaymakersremained________abroad due to the volcanic ash cloud.

Teachers should _____ fundamentals and difficult points in order to enable students toacquire newmaterial. [ ]

下列句中加点词的解释有误的一项是（　　）

My younger brother failed________the exam even though he studied so hard．