— What did the farmer do ________the farm?
— He_______ the chickens.
A:in; feed
B:on; feeds
C:in; feeding
D: on; fed
我国地域辽阔,不同地区的地理环境差异很大.北方地区和南方地区的分界线是秦岭﹣淮河一线,确定该界线的主导因素是( )