For those with Instagram accounts, a person's perceived physical attractiveness is not related to how many followers they have on Instagram, but when we include their self-reported self esteem,we observe that it's strongly related to both their perceived physical attractiveness and the number of Instagram followers they have. What type of causal relationship is there between physical attractiveness and followers?

a. Direct causal

b. Moderated by self esteem

c. Mediated by self esteem

d. Mediated by physical attractiveness

e. Moderated by physical attractiveness