比较对象的一致性，比较对象识别问题，请你解答。

bawenyi

蓝皮书P245 第19题：
   In addition to having more protein than wheat does,(the protein in rice is higher quality than that in)wheat,with more of the amino acids essential to the human diet.
   A. the protein in rice is higher quality than that in
   B. rice has protein of higher quality than that in
   C. the protein in rice ish higher in quality than it is in
   D. rice protein is higher in quality than it is in
   E. rice has a protein higher in quality than
答案为B
 我知道此题考察比较对象的一致性，但是我分不清 这各个选项中对比的到底是 protein 还是 quality  请帮忙分析一下各个选项，谢谢。