关于γ射线下列哪项正确()。
A.在所有的核衰变中均发射
B.每次β衰变时发射
C.当原子核处于激发态时发射
D.每次α衰变时发射
E.电子俘获时发射
参考答案:C
Li Ming is in poor health. He should pay more attention _____ exercise. [ ]
A. to take
B. to taking
C. for taking
D. in taking
简述利用合金化提高金属耐蚀性的途径。