[单选题]
An object is moving with constant n up6-3 1q4uknp5w dn:mznzk1non-zero veaf/c sk9d96wylocity in the +x axis. The velocity ver9fck a/y9swd6 sus time graph of this object is
A. a horizontal straight line.
B. a vertical straight line.
C. a straight line making an angle with the time axis.
D. a parabolic curve.
