PLEASE HELP IF YOU DONT KNOW DONT ANSWER OK THAT NOT WHAT THIS APP IS INTENDED FOR PLEASE GO BY THE RULE OR YOU FACE CONSEQUENCES

Ineed to know why d is the correct answer asap

Creation of an unnaturally uniform sample to represent a diverse populationcan be avoided by: a. including only willing b. asking another scientist for .c. choosing only identical participants.d. selecting individuals at random.

This is a biological reaction due to a stimulus. i need this quickly !