Mark the letter A, B, C, or D to indicate the sentence that is closest in meaningDrugs are tested in patient volunteers to monitor adverse reactions to long-term use.

A. Patient volunteers help test drugs to monitor their adverse reactions to long-term use.

B. Patient volunteers are tested by drugs to monitor adverse reactions to long-term use.

C. Volunteers test drugs for patients to monitor their adverse reactions to long-term use.

D. Adverse reactions to long-term use are monitored after being tested in patient volunteers.