正常老年人脉博次数为:（）

单项选择题正常学龄前儿童脉博次数为:（）

单项选择题Rayleigh’s criterion for resolvability is the angular separation of the two point sources satisfied the condition in which the central maximum of the diffraction pattern of one source is centered on the first minimum of the diffraction pattern of the other. （ ） A. 对 B. 错