产生糖尿病的主要原因是?()
A.B细胞分泌胰岛素不足
B.A细胞分泌胰高糖素不足
C.A细胞分泌胰岛素不足
D.B细胞分泌生长抑素不足
E.D细胞分泌生长抑素不足
参考答案:A
在极坐标系下,圆ρ=2cosθ的圆心到直线ρsinθ+2ρcosθ=1的距离是( )。
It was along the Mississippi River ____ Mark Twain spent much of his childhood _____ the story happened.
[ ]
A. which; that
B. that; which
C where; that
D. that ;that