Which of the following is true of Internet-based health interventions?
a. Many behavioral interventions of this nature aim to help people increase their exercise and improve their diet.
b. Controlled studies of the effectiveness of these interventions show that they are ineffective in helping people change their behaviors.
c. They are not helpful for those who do not have access to in-person programs.
d. Though the Internet helps deliver exercise and nutrition programs to large segments of the population, the costs associated with it are often prohibitive.