Which one alters thoughts and perceptions without any sensory stimulus?

Options

A. Sedative and tranquillisers
B. Cocaine
C. Opiate narcotics
D. Hallucinogen

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a type of substance that alters thoughts and perceptions without any sensory stimulus. This means we are looking for a drug that can change how a person thinks or perceives reality without external sensory input.

2. **Identifying the Drug Category**: The type of drug that fits this description is known as a "hallucinogen." Hallucinogens are substances that can cause significant changes in perception, mood, and cognitive processes.

3. **Effects of Hallucinogens**: Hallucinogens can induce a dream-like state, which is often disconnected from reality. They can alter an individual's mood and behavior, leading to experiences that are not based on actual sensory stimuli.

4. **Examples of Hallucinogens**: Some well-known hallucinogens include:
- **LSD (Lysergic Acid Diethylamide)**: This is derived from the fungus Claviceps purpurea and is one of the most famous hallucinogens.
- **Bhang**: This is made from the dried leaves of the Cannabis sativa plant and is also classified as a hallucinogenic agent.
- **Charas and Ganja**: These are also derived from Cannabis sativa, with Charas being the sticky secretion and Ganja being the inflorescence and green leaves.

5. **Conclusion**: Therefore, the answer to the question is that hallucinogens are the substances that alter thoughts and perceptions without any sensory stimulus.

### Final Answer:
**Hallucinogen**

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