下列说法中正确的是（ ）
A．射线AB和射线BA是同一条射线
B．延长线段AB和延长线段BA的含义是相同的
C．延长直线AB
D．经过两点可以画一条直线，并且只能画一条直线
A、射线用两个大写字母表示时，端点字母写在第一个位置，所以射线AB和射线BA不是同一条射线，此选项错误；
B、延长线段AB是按照从A到B的方向延长的，而延长线段BA是按照从B到A的方向延长的，意义不相同，故此选项错误；
C、直线本身就是无限长的，不需要延长，故此选项错误；
D、根据直线的公理可知：两点确定一条直线，故此选项正确．
故选D．
| 选择恰当的词或短语完成句子。 | |
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