电焊机绕组()必须完好可靠。
参考答案:绝缘
—There isn't _____ good on TV. Let's go to the park.
—Good idea! [ ]
A. something
B. nothing
C. everything
D. anything
发现二项式定理的人是()
A、牛顿
B、哥白尼
C、伽利略
D、开普勒