I can never forget the days _____ we worked together and the days _____ we spent together.A. when; which B. which; when C. what; that D when; when
To protect the environment, the local government has put up a lot of ______ to warn the citizens not to litter the ground.
Corruption is _______ problem in countries across the world, with developing countries often believed to be more serious, although there is no evidence to suggest this is _______case.
— How much influence will your time in high school have on the rest of your life? — It ______ be quite a lot, or perhaps only a little.
If Peter had not hurt his leg, he ______ the important meeting last week.
______ yourself, you should never put convenience before safety.