The chief engineer of the high-speed railway ________ Shanghai to Beijing always devotes most of his time ________ his work.
A:connecting; to
B:connects; to
C:connected; on
D:connect; on
选出不同类的一项( )
物种A的化石比物种B在较晚地层中发现,那么( )
①秦朝的都城是____。
②秦长城西起____;东至____。