many people want to buy it beacuse,-- ,the price is low,--,i

many people want to buy it beacuse,__ ,the price is low,__,it's rather durable.
A.on one side;on the other side
B.for one thing;for another
C.on the one hand;on the other hand
D.in one part;on the other part
为什么选B,不会的真的不会要回答我,看好多人在网上还选A.
随跟我解释下其他几个怎么错了,我觉得都没差啊.