导致脊髓灰质炎的病原是（）
A.脊髓灰质炎病毒
B.肠道病毒
C.柯萨奇病毒
D.腮腺炎病毒
E.以上均不是
参考答案：A
During the 1890s,Henry Ford spent long hours working on his new car in a shed behind his home, ____his neighbors to call him “Crazy Henry”.
A．only to cause
B．to be caused
C．causing
D．having caused
各种信号机及表示器，在正常情况下的显示距离调车：不得小于（）
A.100m
B.150m
C.200m
D.250m
