当别人帮助了你, 你应该说 ____A. OK. B. Nice to meet you. C. Thank you.
It’s _____ hard problem for the twins that ____ of them can work it out.
You ______ to the party if you’re so busy.
—_____I use your dictionary, Tom? —Of course, you _______
Simon improved his way of study. ________, he has made great progress.
—What color is _______ orange? —It's____ orange.