复种指数是指一定时期内(一般为1年)在同一地块耕地上种植农作

复种指数是指一定时期内(一般为1年)在同一地块耕地上种植农作物的平均次数,即年内耕地上农作物总播种面积与耕地面积之比。复种指数的大小受自然因素和社会经济因素的综合影响。读19992013年我国局部地区平均复种指数图(图9),回答2123题。

21.①地是

A.东北区       B.甘新区   

C.华中区       D.西南区

22.长江中下游区复种指数较高,其主要影响因

素是

A.热量         B.光照   

C.土壤         D.海拔

23.华南区复种指数比黄淮海区低,其原因可能

    A.水源短缺     B.旱涝灾害频繁   C.经济水平高      D.科技水平高

答案

AAC

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