作业时,作业人的双手应始终握持绝缘杆保护环以下部位,并保持带电清扫有关绝缘部件的()。
A.完好;
B.清洁和干燥;
C.距离;
D.清洁
参考答案:B
8. Obama’s father was among the first to settle in _______ is known as the most fantastic tourist attraction — Hawaii.
A.where
B.what
C.which
D.That
关于X线管焦点的叙述,错误的是
A.实际焦点是阴极电子撞击阳极靶面的面积B.有效焦点为长方形C.实际焦点面积大于有效焦点面积D.旋转阳极管阳极倾角为12°~19°E.实际焦点越大输出功率越小