—Are you satisfied with what he did?—No. It couldn’t have been _____.
She felt very upset ___________ what her deskmate said.A because B because of C as if D unless
When the expression first came into being, people refused (拒绝)to use it but _____ they began to accept it.
Scientists say it may be five or six years _______ it is possible to test this medicine on human patients.
---Mike, please don’t forget to turn off the light when you leave.---Pardon?---I ________ forget to turn off the light.
It is so nice to hear from her. _______, we last met more than thirty years ago.