—Which of the two cameras are you going to buy?
— I'll buy______ of them because I want to give one to my best friend.
A:all
B:both
C:neither
D:either
①会导致消费者对粮食的需求量急剧增加
②会挫伤农民种粮的积极性
③会导致粮食的单位面积产量不断降低
④会降低低收入居民的生活成本