Why are there misconceptions about orientation and identity?

Which of the following identifies the main culprit for america’s increasing weight gain?

Knowing if a patient has tuberculosis, hepatitis b, or aids is important because a. serious illnesses should be avoided. b. they could compromise the vital sign readings. c. cross-infection may occur. d. they can't be cured.

Can someone give me one specific health problem (within unhealthy eating) and explain it. !