【单选题】What do some scientists say about taking medicines for the common cold according to the passage?
A.
It is good for people.
B.
It actually does more harm than good.
C.
It can help people keep healthy.
D.
It can give them more energy.
【简答题】自然界的甾族化合物,都具有环戊烷多氢菲的基本母体结构: 试指出该结构中有几个手性碳原子,理论上应该有几个旋光异构体?为什么从自然界获得的甾族化合物其旋光异构体数目只有两种构型,大大少于理论数?这两种构型如何表示?
【判断题】如果用钢丝绳夹制作绑扎钢丝的接头,绳夹的鞍形部分应装在活动载荷段,"U”形螺栓应装在静载或缩短端段
【判断题】甾族化合物的基本结构为环戊烷并多氢菲,四个环分别用A、B、C、D表示,C11和C13上常有甲基(称为角甲基),C17上有一个不同碳数的碳链。
【单选题】------How do you like the film we saw yesterday ? ------________, I am pleased with it though some parts are boring.
【判断题】如果用钢丝绳夹制作绑扎钢丝的接头,数量不得少于三个,其间距不小于15Omm