Photographs can document evidence of abuse. a best practice for taking photos of injuries is:

The best practice for taking photos of injuries is to include the victim's face in at least one photo.

Explanation:

In order to report abuse and ultimately stop it from recurring, it is of utmost importance to document the evidence of abuse. Without concrete evidence, like photographs, which is document shortly after abuse has happened it can be very difficult to prove the fact of abuse.  

Victims face has to be present on at least one of the photos taken in the same setting and in a sequence so that police and further court could be convinced that this particular person became a victim of abuse, and not someone else.

i would say b. research typically uses a variety of sources

they could find out our specific needs.