晶体二极管是用（）材料制成的电子器件。
A、导体
B、绝缘体
C、半导体
D、光纤
参考答案：C
As soon as Fei Junlong and Nie Haisheng came back from space, _____reporters interviewed _____and got some first-hand information.[ ]
A. two thousand; they
B. thousands of; them
C. thousand of; their
D. thousands; theirs
具有激肽样作用的补体片段是（）。
A.C5a
B.C2a
C.C4b
D.C3a
E.C3b
