Why Is It Necessary to Study a Sample of Individuals

Multiple Choice

Why is it necessary to study a sample of individuals that is representative of a larger population?

A) ​because a sample gives better statistical strength than a population, and this allows a research to "confirm" any hypothesis (s) he has made
B) ​because there are ethical restrictions against gathering data from a population, but not a sample.
C) ​because a population will include too many people who would be unwilling to answer questions honestly.
D) ​because it would be impractical, perhaps even impossible, to attempt to gather data from an entire population of individuals.