电连接线夹内无杂物，线夹与被连接导线的接触面光洁无（）并涂（）。
参考答案：氧化膜、导电介质
In the last few years thousands of films______ all over the world.[ ]
A. have produced
B. have been produced
C. are producing
D. are being produced
硬粒型玉米通常比马齿型玉米的子粒品质要好。
