Most of the Europeans refuse to accept GM food________Americans regard it as the fruit from high tech. A.when B.as C.while D.the moment 答案:C while表示“对比”。 在匀强磁场中有一个原来静止的放射性的碳14,它所放出的粒子与反冲核的径迹是两个相切的圆.两圆直径之比为7:1,如图所示.那么碳14的衰变方程是146C→0-1e+147N146C→0-1e+147N.