改错。

     Swimming is very popular in summer.

People like swimming in summer because of                                       1.__________

water makes people feeling cool. If you                                              2.__________

like swimming and swim in a wrong place,

it may not be safely. These years, more than                                       3.__________

nine hundreds children died while they were                                        4.__________

having a good time in the water most of                                              5.__________

them were students.

正常人一般肾窦的宽度占肾脏的比例是

A．均是1/2
B．＞2/3
C．＞1/3
D．1/2～2/3
E．均是2/3