下列方程中代表单叶双曲面的是()。
A.
B.
C.
D.
参考答案:A
—Bob, look what you have done! You ruined the experiment.
—It’s not my fault. I just carried out the instructions _____.
A.as told
B.as telling me
C.as telling
D.as I told
精馏是化工生产中常用液—液分离手段。