Principally because of _____, almost all of Canada’s cultivated

Principally because of _____, almost all of Canada’s cultivated land lies within 500 kilometers of its southern border with the United States.
A、population
B、topography
C、latitude
D、climate
【正确答案】：D
【题目解析】：
答案选D。Principally because of climate, almost all of Canada’s cultivated land lies within 500 kilometers of its southern border with the United States.参见教材P278。