第22题:[单选题]信号系统主要有( )组成。 A.A. 道岔、信号、联锁 B. B.信号、联锁、调度集中 C.C. 闭塞、联锁、调度集中 D.D.道岔、信号、闭塞 参考答案:C
第23题: [单项选择]Why does the author mention "a crow" in line 12 A. ( to indicate the size of Archaeopteryx B. ( To specify the age of the Archaeopteryx fossils C. ( To explain the evolutionary history of Archaeopteryx D. ( To demonstrate the superiority of the theropod to Archaeopteryx 参考答案:A