John, an african american student, has chosen to incorporate exercise into his daily routine and to reduce the amount of salt in his diet after finding out that his blood pressure is high. his decision to

His decision to make these lifestyle changes is most likely based on his knowledge that they have higher rates of hypertension and obesity.
High amounts of salt can lead to many problems in anyone's body, this doesn't only refer to African Americans. However, if John doesn't exercise, he might get fat because he may be prone to obesity. 

They both determine the exact age of rocks.