Which one of the following is a mismatched pair of the drug and its effect ?

Options

A. Amphetamines - CNS stimulants
B. Lysergic acid diethylamide (LSD) - Psychedelic (hallucinogen)
C. Heroin - Depressant, slows down body functions
D. Barbiturates - Tranquilliser

Explanation

To determine which pair of drug and effect is mismatched, we need to analyze each option provided in the question.

### Step-by-Step Solution:

1. **Identify the Drugs and Their Effects**:
- We have four pairs to evaluate:
1. Amphetamines - CNS stimulants
2. LSD - Psychedelic
3. Heroin - Depressant (slows down body functions)
4. Barbiturate - Tranquilizer

2. **Evaluate Each Pair**:
- **Amphetamines**: These are known to be CNS stimulants, which means they increase the activity of the central nervous system. This pair is **correct**.
- **LSD**: This drug is classified as a psychedelic or hallucinogen, which alters perception and affects the senses. This pair is **correct**.
- **Heroin**: Heroin is indeed a depressant, which slows down body functions. This pair is **correct**.
- **Barbiturate**: Barbiturates are also classified as depressants, but they are often referred to as sedatives or tranquilizers. However, the term "tranquilizer" can be misleading as it generally refers to a broader category that includes various types of sedatives. This pair is **mismatched** because while barbiturates can have tranquilizing effects, they are primarily classified as depressants.

3. **Conclusion**:
- The mismatched pair is **Barbiturate - Tranquilizer**. Barbiturates are primarily depressants and not specifically tranquilizers.

### Final Answer:
The mismatched pair of the drug and its effect is **Barbiturate - Tranquilizer**.