双烯选择加氢催化剂是利用（）加热氢气来还原的。
A.脱氢反应加热炉
B.导热油
C.脱氢开工加热炉
D.蒸汽
参考答案：C
_____, it was very difficult, but about an hour later it became easier.[ ]
A. In the end
B. At the end
C. At the beginning
D. In the beginning
边缘系统包括
A．扣带回
B．海马回
C．颞横回
D．钩回
E．杏仁核
