The correct answer is D. 4
Step-by-step explanation:
In research, a causal approach is a research method used when the variables the researcher is studying have a cause/effect relationship. This means one of the variables originates the other (cause) or it is the consequence (effect). For example, if the researcher is studying the effects of literacy rate in access to job opportunities, the approach is causal. In this context, to use to approach it is key that the researcher wants to show one variable or factor determines the other through a cause/effect relationship. Thus, this is used when "the researcher must show that one variable determines the values of another variable".