How Might a Researcher Determine Whether a Particular Cultural Belief

How might a researcher determine whether a particular cultural belief serves as a buffer against mortality concerns?

A) by randomly assigning people to think about that cultural belief or not, and then measuring their level of self-esteem
B) by measuring the extent to which fears of death positively correlate with the level of that belief
C) by randomly assigning some people to think about death, and others not to, and then measuring the extent to which people express support for that cultural belief
D) by manipulating the extent to which people connect their sense of self-esteem to that cultural belief, and then measuring the extent to which they are thinking about death