Dr. Jones is conducting a study in which he is observing how parents play with their children. When training his research assistants, he tells them to document how many times the parents smile at their children, frown at their children, encourage their children, and correct their children. This is most clearly an example of

a coding system

Explanation:

A coding system could be defined as using signals to get or transmit information to be used for a study. In some scenario, signal may not be primarily used but data recorded used instead. Dr Jones method of gathering information as regards the research is known as a coding system.

d.) continue to rise rapidly