It ________ we had stayed together for a couple of weeks ________ I found we had a lot in common.
My sister-in-law is the ______ of the information, so it cant be false.
--I believe that more effective measures have to be taken before we can breathe cleaner air. --______. Air pollution has become too serious a problem.
Only when our project has been approved of by the committee ______ to carry it out.
We are lucky to be among the generation of people who have ______ and experienced the great social changes in our country.
______ economic, political and cultural difference, China and America have decided to cooperate in dealing with global issues.