To knowingly allow oneself to pursue unhealthy habits is compared by Fries and Crapo to

A．current medical knowledge is still insufficient.
B．there are many factors influencing our decisions.
C．few people are willing to trade the quality of life for the quantity of life.
D．people are usually influenced by the behavior of their friends.

A．personal health choices help cure most illnesses.
B．it helps raise the level of our medical knowledge.
C．it is essential to personal freedom in American society.
D．wrong decisions could lead to poor health.

A．personal decisions.
B．society's laws.
C．statistical evidence.
D．friends' opinions.