18.

Variable ratio refers to the schedule underlying which a different number of behaviors is being followed by the consequences. For example, praising employees only for the extraordinary performance. In this case, A made effort to complete the work on the day it is being allotted to her, thus it represents that one consequence resulted in different behavior on the part of A to finish the report by the end of the day. Hence, it is ascertained that the theory represented by the statement is “Variable ratio”