[单选题]
An object is moving with consta+9sb3gs+pt8f vy h8stnt non-zero acceleration in the c a mkyyunsm h*74- 78fr*p8gs+x axis. The position versus 7sy-ruphn7m a48skc f* *g8my 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.