Answer:
A. Did not refer to the source of the information in the body of the post
Step-by-step explanation:
In the post written by his friend, we can see that he decided to write information about the periodic inspections carried out by the United States Department of Agriculture as well as by the Food and Drug Administration, because he read about these inspections somewhere. However, he forgot to show this place where he read this information, that is, he forgot to present the source where he got the information presented in the post. By presenting the source, it would make the post more trustworthy and relevant.