[单选题]
The gamma factor is defin2,st qf+1e)i t uox38vxqrwd(ov+t 7 ned ast0dfs1;a g k8uz ;4qvm $\gamma = 1 / \sqrt{1- (v/c)^2}$, therefore gamma ($\gamma$)
A. can be zero.
B. can be any number less than or equal to one.
C. can be any number greater than or equal to one.
D. cannot equal one.