关于连杆杆身的正确说法是（）。
A．杆身截面均为圆形
B．杆身截面均为"工"字形
C．杆身要有足够的抗拉强度
D．杆身要有足够的抗弯强度
参考答案：D
Mary’s skirt looked just the same as Joan’s, but it cost __________ hers.
A．as much twice as
B．twice as much as
C．much as twice as
D．as twice much as
碳四塔回流泵全坏，操作调整正确的是（）。
A、碳四塔改全回流操作
B、关闭碳四塔热源
C、脱丙烷塔底直接改出装置
D、切断碳四塔与脱丙烷塔的流程
