驾驶自行车、电动自行车、三轮车横过机动车道时不下车推行的，责令改正，处警告或者（）元罚款。
A.5
B.10
C.20
D.50
参考答案：D
A．该圆板是非晶体
B．该圆板是多晶体
C．该圆板是单晶体
D．该圆板的导电性是各向异性的
What may be the oldest fossil footprint yet found was discovered in June 1968 by William J. Meister, a non-professional fossil collector.
A．a part-time
B．a spare-time
C．an untrained
D．an amateur
