[单选题]
A photon is a particle ).:m agq(qjghk u(v(athatmf573iike y -g t: i2 u;dfex:th4mq,h
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