[单选题]
If the velocity versus time graph of an object iov i4g :67vezxs a s02ra;k uficxp 7n)bkl (h 8c(vtraight line making an angle of 30 degrees2kcrv8bn;(i x0pl ( )7achkfu with the time axis, the object is
A. moving with constant non-zero speed.
B. moving with constant non-zero acceleration.
C. at rest.
D. moving with infinite speed.