When were you born?—I was born _________.

Mary ________ her homework last night because she was ill.

Whenever I go to Beijing, ____ is quite frequent, I will go to visit the Great Wall.

Why didn’t you call me this morning?——I ______ call you. I called you all the morning, but I couldn’t ______.

The teachers often tell their pupils _____ across the road when the traffic light is red.