休克（）.
A.肺性发绀
B.混合性发绀
C.淤血性发绀
D.缺血性发绀
E.心性混血性发绀
参考答案：D
_____ the scientist could clone people? I can't imagine. [ ]
A. How about
B. What if
C. What about
D. What
煤按可燃基挥发分可以分为（）、（）、（）和（）四种。
