Canada has vast areas of wilderness, from the Arctic north, _______ average winter temperatures are usually -20 ⁰C, to the border with the USA in the south, _______ is said to be the longest border in the world not defended.

A．which, where

B．whose, which

C．where, where

D．where, which

在人体内不能自行（）或（）的速度远不能满足机体的需要，必须从食物中摄取的氨基酸称为“必需氨基酸”。