Months after last taking a drug, a former drug abuser still produces very little serotonin. the person is depressed and anxious and has great difficulty remembering new material. most likely, the abused substance was: a) ecstasy.
b) cannabis.
c) lsd.
d) benzodiazepine.

Ecstasy

Explanation:

It is called as Molly and is a very know psychoactive drug which is used as as a recreational drug.

The effect includes altered sensations, empathy, pleasure and increased energy.

It is taken orally and it shows its effect in 30 to 40 minutes after the drug is taken and lasts for 3 to 6 hours. The longer effects of this drug results in decreased level of serotonin and the person stays in depression for a longer period of time.

The person might have taken ecstasy.

the answer to your question is:

c. complementary base-pairing