单项选择题
一质点沿x轴作直线运动，其v-t曲线如图所示，如t=0时，质点位于坐标原点，则 t=4.5s 时，质点在x轴上的位置为
A.
5m
B.
2m
C.
0
D.
-2m
一质点沿x轴作直线运动，其v-t曲线如图所示，如t=0时，质点位于坐标原点，则 t=4.5s 时，质点在x轴上的位置为
A.
5m
B.
2m
C.
0
D.
-2m
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