I was about to leave the office ______ an unexpected visitor came.A. while B. as C when D. before
the website of China Daily, and you will learn more about it.
____ has helped to protect the environment is worth praising.
—Why didn’t Tom go to the concert last night ? — I have no idea, but I think he _____ in his study.
Being examined twice a year is the rule that every driver _____ obey in this city.
I’m calling to ask for information about the position____ in the local TV news.