Nature reserves are very important for preserving many animals and plants, which would _______ run the risk of becoming extinct.

Failure hurts adults and children ______ , but it can make a positive contribution to your life once you learn to use it.

He said he would come . He didn't _______.

The famous professor’s lectures, though ____ informal, are considered far more informative and interesting.

------ Who knows the meaning of the saying “ Time __________ will tell.” ------ __________ Tom knows.