请教PREP 54

54.  (27343-!-item-!-188;#058&003156)

Unlike using spices for cooking, in medicinal usage they are taken in large quantities in order to treat particular maladies.

(A) Unlike using spices for cooking, in medicinal usage they are taken

(B) Unlike spices that are used in cooking, in using spices for medicine, they are taken

(C) Unlike cooking with spices, taking spices for medicinal use is done

(D) In cooking, small quantities of spices are used, whereas in medicinal usage spices are taken

(E) In cooking, the usage of spices is in small quantities, whereas in medicinal usage they are taken

我对这道题目的答案D没有异议，但是想问一下E选项中的they不能错误的指代spices吗？我的意思是说，they不可能犯的是指代错误吗？为什么解释说是没有指代对象呢？谢谢大家。