Blood alcohol content (BAC) is a measure of the amount of alcohol that is present the blood.
A heavier person will have a lower blood alcohol level due to a greater amount of water in their body. The more a person weigh, the more water he/she tends to have in his/her body. The water has a diluting effect on the alcohol so the BAC will be lower in comparison with person who is slimmer and has less water in the body.
Infection is not a controllable health factor. The correct option among all the options given in the question is option "b". The other options given in the question is definitely controllable by an individual. Infection can get into a person without his or her knowledge. This infection can be fatal under certain circumstances and so infection always needs to be controlled.
