Currently in development are vaccines that researchers are developing to help prevent relapse in people addicted to cocaine. These vaccines are designed to:

• A. stimulate the immune system to produce antibodies that bind cocaine.
• B. cause immediate vomiting and nausea when cocaine is used.
• C. directly reduce craving and withdrawal symptoms through neurotransmitter replacement.
• D. permanently block brain receptor sites that normally bind cocaine.

Answer: (A)