I think _______ is really difficult for us to work out this kind of math problem.
| A．it | B．this | C．that | D．one |
—Could I borrow your computer. Bob?
—Sorry, I am______ it.
A. taking out B. turning on C. working on
Dear students, please read every sentence carefully. The more _____ you are, the______ mistakes you'll make.
A. carefully; fewer B. careful; less C. careful; fewer
Please follow _____ I say.
A. what B. that C. which
—My old friend White is going to visit me.
—We haven't seen each other_____ five years.
A. since B after C. for
—I ______ something wrong just now. May 1 use your eraser?
—Of course. Here you are.
A. write B. wrote C. am writing