—Why didn’t you put your cellphone in your overcoat pocket?—I ________, but I was afraid it would be stolen.

— What does the notice on the wall say? — “No person _____ take books out of the reading room; otherwise he _____ be fined.”

I know it’s normal for such a thing to happen, but we _____ it if we’d been more careful.

. If only I ________ how to operate an electronic computer as you do. 

I don’t know why she suggested that we _____ the work before dark.