In order to assess whether viewpoints on decriminalization of marijuana for medical purposes change with age, four groups of participants, ages 20, 30, 40, and 50, are asked whether they support this issue. what is one flaw of this design? select one:
a. longitudinal research is time-consuming.
b. marijuana has already been decriminalized in some places.
c. recruitment could be a challenge because people of different ages are difficult to sample.
d. social or cultural factors may influence the results, not age.