Things made of plastic are usually but they are to get polluted.A. cheap; easyB. cheap;

问题补充：

Things made of plastic are usually , but they are to get polluted.

A. cheap; easy

B. cheap; easier

C. cheaper; easy

D. cheaper; easier

答案：

A. cheap; easy

B. cheap; easier

C. cheaper; easy

(答案→)D. cheaper; easier

解析：根据句意可知塑料制品相对比较便宜但是也会带来污染，有比较之意故选D.