旅客不能按票面指定的日期、车次乘车时，在不延长客票有效期的前提下，可以办理一次提前或改晚乘车签证手续。（部竞赛题）
参考答案：错
Since the baby milk powder was found to be polluted, there has been universal doubt _____ other food products are safe _____.
A．that; to eat
B．whether; to be eaten
C．whether; to eat
D．that; to be eaten
在胸部X线片上出现的Kerley-B线（在胸片上肺下野或肺门旁的细线）说明存在下列哪种情况（）
A.左心衰所致的肺淤血
B.胸腔积液
C.老年性肺气肿
D.肺动脉狭窄
E.梅毒性主动脉炎
