The flat rent is expensive, I’ve got about half the space I had at home but I am paying ________ here.

A．at twice much

B．as much twice

C．much as twice

D．twice as much

用图示装置制取少量乙酸乙酯（酒精灯、铁架台等在图中均已略去），请填空：

（1）写出试管a中发生反应的化学方程式______

（2）某同学在实验过程中，试管a中忘记加入碎瓷片就加热进行实验，为防止暴沸，下一步的操作是：______．

（3）实验中加热试管a的目的是：①：______②：______

（4）反应结束后，振荡试管b静置，观察到的现象是______．