A:①②④
B:①②③
C:①②③④
D:①③④
—Why didn't your sister talk with me?
—She is a _______ girl. She is afraid of speaking before strangers (陌生人).
甲、乙两列火车在两条平行的铁轨上匀速行驶,两车交汇时,甲车座位上的乘客从车窗看到地面上的树木向南运动,看到乙车向北运动.由此可判断()