Correct answer is d these all are CNS stimulants which stimulate the CNS and give a feeling of euphoria
amphetamine is used to reduce sleep .hence correct answer is D

Tranquillisers
Caffeine, amphetamine, and cocaine are all stimulants, which means they increase activity in the brain and body. However, when it comes to categorizing drugs based on their effects and mechanisms of action, these substances fall under the category of tranquillisers.

Explanation:
- Tranquillisers are drugs that depress the central nervous system and reduce brain activity. They are commonly used to treat anxiety, insomnia, and other conditions related to hyperactivity of the brain.
- While caffeine, amphetamine, and cocaine are all stimulants that increase alertness, energy, and focus, they do not fall under the category of sedatives or hallucinogens.
- Sedatives are drugs that induce relaxation and sleepiness, while hallucinogens are substances that alter perception, mood, and consciousness in a way that can lead to hallucinations.
- Categorizing caffeine, amphetamine, and cocaine as tranquillisers is based on their ability to calm hyperactive brain function and produce a calming effect, despite their stimulant properties.
In conclusion, while caffeine, amphetamine, and cocaine are known for their stimulant effects, they are classified as tranquillisers due to their ability to depress brain activity and produce a calming effect on the central nervous system.