I called you, but nobody answered. Where ________ you? [ ]
A. is
B. are
C. was
D. were
答案:D
在焊接工作时,焊接管子管端硬度应()管板。
A、大于
B、等于
C、小于
D、大于等于
丝绸与玻璃棒相互摩擦后,玻璃棒带____________(正/负)电,将丝绸靠近带负电的轻质小球时会相互____________(排斥/吸引).