Which of the following best expresses the main idea of ale passage
A．Research has suggested that the neurotransmitter serotonin is responsible for the effects of hallucinogenic drugs on the brain ant on behavior.
B．Researchers have spent an inadequate amount of time developing theories concerning the way in which the effects of hallucinogenic drags occur.
C．Research results strongly suggest that hallucinogenic drugs create their effects by acting on the serotonin receptor sites located on target neurons in the brain.
D．Researchers have recently made valuable discoveries concerning the effects of depleting the amount of serotonin in the brain.