Similarities between bulimia and anorexia include: a. both tend to begin after a period of dieting among people afraid of becoming obese. b. both involve a reluctance to think about food, weight, or appearance. c. both involve an underestimation of one's weight and body size. d. both tend to be related to personality disorders.

The bulimia is associated with the emotional disorder that involves the obsessive desire to loose weight to retain a desired body image. The person favors dieting, avoids overeating, person avoid fatty foods. This person indulge in self-induced vomiting, fasting and purging to retain the desire body shape.

Anorexia is an eating disorder, which also causes people to get obsess about the weight. The anorexia is characterized by fear getting overweight. The anorexia is different from bulimia as in this the person avoids eating food and prefer starvation. The person uses over-exercise to reduce weight.

According to the given information, a. is the correct option as in both cases the people are afraid of gaining weight or becoming obese. This begins after the period of dieting and the person tries to avoid food, balance diet in both cases.