键相器探头是依据（）原理工作，应安装于径向位置。
A.压电效应
B.光电效应
C.电磁感应
D.光敏效应
参考答案：C
She thought I was talking about her daughter, ____ in fact, I was talking about my daughter. [ ]
A. when
B. whom
C. which
D. while
选用一种试剂就能非常简便地鉴别稀盐酸．氢氧化钠．氢氧化钙三种无色溶液，这种试剂是______
