阅读短文，用合适的单词完成句子。

     John is a paper boy. He delivers (送) newspapers to different houses in his street every day. He

has about 80 customers (客户). Half of his customers only take the newspapers on weekdays, and

about half take the newspapers on weekends. Two of John's customers only take the newspapers on

Sundays.

     John has to get up at 4:30 every morning to deliver his newspapers on Sundays.

     John is saving his money to buy a new bike. He is also saving money for college. He has $500 in

the bank now.

1. John delivers _____ every day.

2. John has about _____ customers.

3. _____ of his customers only take the newspapers on Sundays.

4. John is saving his money to buy _____.

5. "Paper boy" in this story means "_____ in Chinese.

钻井四通主要用于连接防喷器和（），侧口连接放喷或压井管线。

A、套管底法兰

B、环形防喷器

C、旋转防喷器