Though ______, many laws of nature exist.
A.not having been discovered | B.having not been discovered |
C.not having discovered | D.having not discovered |
Young students are ______ not to smoke both in and out school.
A.suggested | B.requested | C.hoped | D.invited |
He commanded that all the gates _____when it was getting dark in case thieves came in .
A.were shut | B.must be shut | C.could be shut | D.be shut |
Mr. Black has been teaching English in a middle school _____ he came to China.
A.for ever | B.ever since | C.ever before | D.long before |
. — What's that noise?
—Oh , I forgot to tell you. The new machine ________
A.was tested | B.will be tested |
C.has been tested | D.is being tested |
—Sorry. I didn’t break the plate______.
—It’s OK. Don’t worry about it.
A.on purpose | B.no longer | C.at present | D.as usual |