Frank is looking forward ______ his pen pal[ ]

Why didn’t you attend the lecture yesterday?—I didn’t think that we _______ on Sundays.

The experiment shows that proper amounts of exercise, if ______ regularly, can improve our health.

Students ________________slippers(拖鞋) when they are at school.

___ he came to study in the university, he has made much progress in the study of English