The correct option is B.
A positive feed back refers to the amplification of a particular effect by its own influence on the process that gives rise to it. In positive feed back, the specific response that is obtained as a result of a process continue to increase as the process continues or increase, that is both the process and the effect generated increase.
Answer and Explanation:
Observing population directly gives you accurate result .
Direct observation does not need any intermediary as they themselves go for survey.
So, it is cost efficient.
Whereas indirect observing may involve manipulations.
It requires someone or many to hire who helps in surveying.
It incurs cost.
Thus, direct observation is always better than indirect observation.
