They had camped once before, ____ they knew what to take.
A.because
B.now
C.so
D.since
答案:C
历史上对于中风病的名称还称
A.仆倒
B.大厥
C.卒中
D.偏枯
E.风痱
下列哪个统计量可以描述两个变量的相关关系( )
A.Mann-Whitney U
B.x2
C.wikoxon T
D.t