Doctors say that exercise is important for health, but it ______ be regular exercise.

单项选择题Not until he left his home ______ to know how important the family was for him.

单项选择题Galileo lived in the City of Pisa, ______there is a leaning tower about 180 feet______.

单项选择题Last year the number of students who graduated with a driving licence reached 200,000, a(n) ______ of 40,000 per year.

单项选择题Jim went to answer the phone.______, Harry started to prepare lunch.

单项选择题We only had $ 100 and that was______to buy a new computer.