Be careful when you cross this busy street. _____, you may get run over by a car.
Our teachers often ask us ______ over the answers carefully before handing in our papers.
The window ______ by Tom yesterday. Mr. White is repairing it now.
—Excuse me, Mr. Brown. ______ you speak Chinese?—Yes, butt only a little.
Either she ______ he is fit for the job, but not me.
Most of us found ______ difficult to finish the work in such a short time.