What does the word "chronic" (Sentence 3) mean
A) painful. C) persistent.
B) minor. D) infectious.

A．Only poorly educated people seek the advice of quacks.
B．Quacks are motivated by the desire to help mankind.
C．A person's brain can not control the body's pain-tolerance level.
D．The human brain is a powerful and mysterious organ.

A．people who are in pain will often pay any amount of money for the promise of relief
B．the average person is not trained to evaluate medical claims and diagnoses
C．although their remedies may not cure a disease, quacks nevertheless do not harm their patients
D．quacks convince patients that they can help them