Which of the following is a common technique advertisers use to mislead consumers into using "fad diets" to achieve optimal health and fitness?

a. requiring aerobic exercise
b. using flexibility movements
c. allowing only one or two food types
d. promoting nutritional balance

The correct answer is C.

Advertisers regularly use the technique of selling fad diets to help people lose weight and get fitter by promoting the use of one or two food types. So for example you can only eat meat and vegetables but no carbs, no sugar, no fat etc. They usually get you to supplement these food groups with their own brands of snacks or have ready made meals for you. These diets might work in the short term but overall are not healthy for you and you will not maintain the weight loss.