Many young people in the west are expected to leave        could be life's most important decision

-marriage- almost entirely to luck.    [ ]

A. as          

B. that          

C. which            

D. what

恒星距离的测量方法包括（）

A、三角视差法和雷达

B、三角视察法和分光视察法

C、分光视差法和雷达

D、雷达和多普勒