Answer:
(B) an experiment
Step-by-step explanation:
An experiment typically involves a comparison between two groups (Although some experimental studies have only one group or even three or more groups). It is the most scientifically sophisticated research method and is defined as observation under controleed conditions.
Experimental research design are concerned with examination on the effect of independant variable on the dependant variable, where the independant variable is manipulated through treatment of interventions and the effect of those interventions is observed on the dependant variable.