At what age do children tend to have the lowest BMI?

Some evolutionary psychologists explain altruistic behavior towards individuals that we are not directly related to by noting that altruism towards nongenetic relatives will possibly be returned in the future. This concept is known as

A) diffusion of responsibility. B) the social responsibility norm. C) kin selection. D) reciprocal altruism.

Today, gender roles in the American family are:

A) becoming more flexible. B) becoming more rigid. C) disappearing altogether. D) about the same as 50 years ago.