If nothing________,the oceans will turn into fish deserts.
________ seems to be a strong competition in China for senior high students to enter college or university.
It is no use _________ to persuade him ________ smoking because he has been addicted to it since he was young.
I would have come earlier, but I ________ that you were waiting for me.
five hours to the meeting, David learnt that it had been postponed.
After the new technique was introduced,the factory produced ________ tractors in 1988 as the year before.