Most people in Britain live in small family groups. More than a quarter of homes in Britain have only one person living in them. Some of these persons are old but some are of twenty to thirty who choose to live alone. 35% of homes have two people living in them, and another 17% have three people. 15% have four people living in them, and the other homes have five or more.

The families in Britain are small. It is unusual for parents to have more than two children. When children are about eighteen or nineteen, they leave their parents’ home, and they often go to other cities. Sometimes they only visit their parents two or three times a year.

根据短文内容，判断正(A)误( B)。

小题1:The passage is a report.

小题2:35% of homes in Britain have 3 people living in them.

小题3:The families in Britain are large.

小题4:Some are people of twenty to thirty who choose to live alone.

小题5:The passage mainly tells us the population in American.

流体输送设计中，在满足工艺要求的前提下，尽可能减短管路，目的是

A．增加流速

B．降低流速

C．增加流体的阻力

D．降低流体的阻力