Scientists have many theories about how the universe ___ into being.

It suddenly_____ to me that I could use a computer to do the job.

—Was he still there when you were away to answer the phone?—There is no doubt about it, but he ________ soon afterwards.

I ________ in London for many years，but I've never regretted my final decision to move back to China.

Mary did do some bad things about me, but I have ______ her for that.