单项选择题
The population had______from about 8,300,000 in 1845 to less than 6,600,000.
单项选择题 The factory is said______in a fire two years ago.
单项选择题 My advisor encouraged______a summer course to improve my writing skills.
单项选择题 Having been ill in bed for nearly a month, he had a hard time______the exam.
