It’s D experimental bias because experimental bias is also called experimenter bias which means process where scientists preform real research influence the results in order to portray a cartoon out come
Experimental bias occurs when a scientist performing a research influence the results in order to portray a certain outcome.In this case,Ron unintentionally smiled when then subject was showing to act as expected.In doing so,"smiling" the subject was able to identify the correct answer.
Urban areas doubled, tripled, or quadrupled in size which led to over crowding in cities. Sometimes a large population is a good thing, but in this case the population was too big and caused many health problems.
