Answer:
D. to inform
Explanation:
The best way to describe the author's purpose in writing this piece is "to inform".
Actually, "to inform" simply means to give information for one to get acquainted with something. Here, the author gives the audience an information about herpetologists. He goes further to say what they do and the careers in herpetology. With this information, anyone trying to go for a career in herpetology has a handy information. Also, those that have not heard it before can understand what it truly means.