[单选题]
How fast should a moving clock travel itk qjfjoulr0meej;;+ t, u64 -f it is to be observed by /wcm8 k+kjb(z2y87 m6zixqm ka stationary observer kjk68kmxz2 c/w (iq8+m 7myz bas running at one-half its normal rate?
A. $0.50 \; c$
B. $0.65 \; c$
C. $0.78 \; c$
D. $0.87 \; c$
