一辆汽车在公路上行驶，两次拐弯后，仍在原来的方向上平行行驶，那么两个拐弯的角度（ ）
A．先向左转130°，再向左转50°
B．先向左转50°，再向右转50°
C．先向左转50°，再向右转40°
D．先向左转50°，再向左转40°
如图：
A、∵∠1=130°，
∴∠3=50°=∠2，
∴a∥b，方向相反；
B、∵∠1=∠2=50°，
∴a∥b；
C、∵∠1=50°，∠2=40°，
∴∠1≠∠2，
∴a不平行于b；
D、∵∠2=40°，
∴∠3=140°≠∠1，
∴a不平行于b．
故选B．
| 从方框里选择正确的短语，并用其正确的形式填空。 | |
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