Sophia waited for a reply, but ____ came.
The book isn't intended for general readers probably because the author _______ too many scientific terms(术语) in it.
---- What does P.O._________? ----Poster order, I guess.
It was not until dark __________ he found __________he thought was the correct way to solve the problem.
It is reported that the United States uses ________ energy as the whole of Europe.
--May I put my bicycle here? -- Yes. But you should always keep it ________, in case it is stolen.