Verb tense and aspect：练习题

While I _____ for the bus, I met an old friend from my primary school.

Hardly _____ the stage when the audience began to cheer enthusiastically.

The Earth _____ around the Sun, which is a scientific fact we learned in primary school.

I realized I _____ my umbrella on the train only after I stepped out into the pouring rain.

Look at those dark clouds! I think it _____ to rain very soon.

Complete the following sentence by putting the verb in the brackets into the correct tense:
"She ________ (study) for her exam since eight o'clock this morning."

Identify the error in the following sentence and rewrite it using the correct tense:
"By the time the movie ended, we already ate all the popcorn."