单项选择题
The changes in the city will cost us a lot of money, ______ they will save us money in the future. ( )
单项选择题 I finally got the job I dreamed about. Never in my life ______ so happy. ( )
单项选择题 ______ of years ago, whales lived ______ land and walked on four legs. ( )
单项选择题 The world’s population is becoming ______. ( )
