The water at the bathing beach became______by refuse from the factory.

单项选择题The airline flies aeroplanes to cities like Paris（）

A.day and night, right through the week
B.two or three times a week
C.at any time of the day, but not at night
D.right through the day, two or three times a week

单项选择题According to Richard, the main purpose of running the bookstore is()

A．to pay for their children’s education
B．to get to know more writers
C．to set up more bookstores
D．to do what they like to do