X线管外壳材料应具备的条件不包括
A.热膨胀系数小B.绝缘性能好C.吸收X线多D.能与金属焊接E.承受高真空压力
参考答案:C
解析:C不正确,应是吸收X线少。
—Does he have a tennis racket?
—______. [ ]
A. Yes, he is
B. No, he doesn't
C. No, he does
D. No, he is
简述最大需量电能表的用途。