一下那些物质不容易在骨骼中沉积：（）
A.氟
B.铅
C.锶
D.Hg
参考答案：D
一个圆柱的体积是12.6立方厘米，和它等底等高的圆锥的体积是（ ）立方厘米。
Taobao.com is a free site, ________ visitors can not just purchase almost all kinds of products
but open their own online shops.[ ]
A. whose
B. which
C. what
D. where
