井下供电系统中“三无”指什么？
参考答案：
无鸡爪子、无羊尾巴、无明接头。
Much to the government's disappointment, this year has ____ a big increase in road accidents. [ ]
A. told
B. seen
C. said
D. watched
为使喷涂层粘牢固，最好把裂缝造成（）形槽。
A.W
B.N
C.V
D.L
