The effects of marijuana are?
a. unkown
b. similar to those of cocaine
c. variable
d. both b and c

Variable

Explanation:

Personal experiences led me to this answer. A primary source is the best one. Brainliest me pl :)

out of the choices i'd say d the ability to set goals, mainly because to desire to continue you need motivation but it isn't motivation in that part, but setting goals means you have an endgame and you want to reach it which sums up motivation.