The limits of a person’s intelligence,generally speaking, are fixed at birth, but _____ he reaches these limits will depend on his environment.

This is a problem ____ to work out in two minutes.

Companies often ______ mystery shoppers to inspect their service.

You don’t know about the difficulty I had ______ the work then at all.

I spent half an hour _____ this difficult math problem.

“Why hasn’t he turned up yet?” “He ________ have missed the train, but I’m not quite sure.”

—_________________________—I’m not sure what I’ll do. I hope to watch TV and enjoy myself.

Only after I read the text over again _____ its main idea.

Is there anything ____ I can do for you?

I was annoyed by my friend who came late for our appointment but did not botherto ask how long I ____.