空气的密度比液体密度()。
参考答案:小
The earth became so violent ____it was not clear ____ the shape would last or not.
A.which; whether
B.that; what
C.what; if
D.that; whether
当细过滤器处于()模式下,流量报警信号有效
A、反洗
B、正常操作
C、退出锁定
D、锁定