Until Berta and Ernst Scharrer established the concept of neurosecretion in 1928, scientists believed that either cells secreted hormones, which made them endocrine cells and thus part of the endocrine system, or conducted electrical impulses, in which case they were nerve cells and thus part of the nervous system.
(A) either cells secreted hormones, which made them
(B) either cells secreted hormones, making them
(C) either cells secreted hormones and were
(D) cells either secreted hormones, in which case they were
(E) cells either secreted hormones, which made them
原文意思：直到一个家伙建立了一个概念，科学家相信或者是细胞cecret 荷尔蒙了或者传导电流了
题目分析：原文体现出了1个由either or引导的并列关系，or后面用的是动词conducted +in which的从句，和这个对应的只能是D。这道题不难，就是在either说完之后加入插入语让我们看到either or引导的这个并列难度加大了一些！
