在两部门经济中，如果经济处于IS曲线左下方，那么（）
A.投资等于储蓄
B.投资小于储蓄
C.投资大于储蓄
D.产品市场处于均衡状态
参考答案：C
_______that all mountain roads were closed.
A．So became the dangerous weather
B．So dangerous did the weather become
C．So dangerous became the weather
D．Dangerous the weather became so
管路系统的特性曲线是随着（）的增加而上升。
A、流量
B、扬程
C、轴功率
D、效率
