[单选题]
If the position versu d0iqh.w )qkz(s time graph of an object is a horizonik g yv:sqzl,))s+bwr 56h y0dtal line, the object il s sih, yryd6qz5g )wv+:0b)ks
A. moving with constant non-zero speed.
B. moving with constant non-zero acceleration.
C. at rest.
D. moving with infinite speed.