问题详情

"subtle visual traps" (Line 4, Para. 3) refers to ______.
A．places where the police hide in order to trap motorists
B．dangerous parts of the road which are not easily noticed by drivers
C．danger spots such as sharp corners and cross-roads
D．places where there are too many road-signs请帮忙给出正确答案和分析，谢谢！