题干
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
答案(点此获取答案解析）
A
的球的球面上有三个点，其中任意两点间的球面距离都等于
，且经过这三个点的小圆周长为
，则
