My new pen ______. Who ______ have taken it?
More and more people have a low-C life and the air is_________ than before.
Warmblooded animals live an active life even in freezing winter，which helps them to ________ their normal body temperature.
Only after they had discussed the matterfor several hours ______a decision.
Did you receive the letter the next day?—No Somehow, it was three weeks ________ I received it
