Tom and Mary do homework ______ about five o’clock in the afternoon.

I think it’s impossible for us to work out the plan in just two days. It’s too difficult.—You’re right. We can’t be _______ careful and hard while working on it.

It suddenly ______ to the detective that the professor was probably murdered by his own wife .

Some of my friends are interested in science, but none of them can tell ________.

So many women take up walking as a regular form of exercise every day, which, of course,isto their health.