原子吸收分光光度计中单色器在原子化系统之前。( )
参考答案:错
Harry has two tennis rackets. He takes _____ to school every day.[ ]
A. it
B. these
C. them
对电动机的单相接地保护,当单相接地电流为( )及以上时,保护应带时限动作于跳闸。
A.1A; B.5A; C.8A; D.10A。