People sometimes take life$-$threatening risks $=$ such as not wearing helmets when riding motorcycles, having unprotected sex, sunbathing against a doctor's advice, and driving far over the speed limit$-$in order to "look cool." This best demonstrates the strong power of

a$.$ the fact that "nature says go and culture says stop"

b$.$ self$-$presentation

c$.$ the appraisal motive

d$.$ the automatic system