Which option corrects the error in this sentence?

Question

Jacob wants to adopt a puppy from the local animal shelter because [they say] that mix breed dogs have fewer health problems than purebreds.

A. one says

 

B. he says

 

C. veterinarians say

 

D. No change

Answer 1

Option C. Although I believe there should be an option for "research says..."  

Answer 2

A shelter is an inanimate thing and, thus, NOT a THEY, ONE or HE!

 

If veterinarians do say such a thing, then "veterinarians say" is the essential and only (and correct) choice available!

Answer 3

The answer is C. 

Answer 4

It depends upon what the intended antecedent of the pronoun is.  If the intended antecedent of the pronoun is Jacob, then the answer is B.  However, if the intended antecedent of the pronoun is the local animal shelter, then the answer could be D if the local animal shelter is considered a plural entity.  Otherwise, the answer is not one of your options.  The answer in that case would be "it says".