题干
.
The warmth of ______ sweater will of course be determined by the sort of ______wool used．
The warmth of ______ sweater will of course be determined by the sort of ______wool used．
A：the; the
B：the；／
C：／；the
D：／；／ .
答案(点此获取答案解析）
B
,且 
,则方差为
在点
处的切线与直线
垂直，则
( )