凡是两种色光相混合而成（），这两种色光互为补色。
A.黑光
B.白光
C.黄光
D.红光
参考答案：B
The driver could have survived but he __________ the seat belt. [ ]
A. had been wearing
B. hadn't worn
C. wasn't wearing
D. didn't wear
瓶插固定法有（）固定法等。
A、自然
B、间隔
C、丁字
D、添枝
E、折曲
F、铅丝网
