[单选题]
A photon is a particle tj49o mnndyr .p:se1*h n)+un;9oinu0,hn0 t dg jxxw-pvdo/;hat
A. has zero electric charge.
B. has zero electric field associated with it.
C. cannot travel in a vacuum.
D. has a velocity in a vacuum that varies with the photon frequency.
Post time 2024-1-22 00:41:22