Answer:
All the answers are correct because research is multifaceted
Explanation:
While doing population studies, it is important to understand the population and they demographic, age, sex, location etc. This could have incredible effects on comparative studies.
It is also important to maintain an open line of communication to give instructions and follow up on the persons in the event that this kind of data is required. But like with population study the error that often comes into play is the element of human dishonesty. By keeping an open line of communication, the provisions can be made to keep this under check.
Finally, making sure that all the participants understand what is being asked of them is key to the open line of communication as not to create any misgivings or misunderstanding.