One research team studied the ups and downs of human moods by counting positive and negative words in 504 million Twitter messages from 84 countries. The researchers' method best illustrates the use of

a) experimentation.

b) naturalistic observation.

c) case studies.

d) a survey.

Answer:b) naturalistic observation

Explanation:

Naturalistic observation is based on carrying a research which observes subject in their natural environment without any intervention from a researcher. It is usually conducted when doing a lab research will be unreasonable or unrealistic or will interrupt the natural behavior of the subject. People are more relaxed in their natural habitat than when they are in a constrained environment such as a lab where they may feel like they need to change their behaviour to conform to what the research is about.

When people are watched in their natural environment they are likely to act in a normal way as they always react in real life which will give a research a true presentation of how they react to a particular situation in real life.