巴比妥钠注射液中加入丙二醇而增加稳定性，其原理是 A．增大介电常数 B．减小介电常数

如果m，n为实数，且满足|m+n+2|+（m-2n+8）²=0，则mn=______．

There is a popular view       in cities, strangers are less likely to help an elderly person.

A．that

B．whether

C．why

D．how

我国少数民族中，人口最多和最少的是（    ）

A．壮族、珞巴族

B．壮族、高山族

C．回族、高山族

D．汉族、珞巴族

If you _________ my advice, you ________ your failure now. You _________ your victory.[ ]

A. took ... wouldn't cry over ... would celebrate

B. had taken ... wouldn't have cried over ... would have celebrated

C. had taken ... aren't crying over ... are celebrating

D. had taken ... wouldn't be crying over ... would be celebrating

当发现跨步电压时，应两脚用大步尽快离开危险区。