The catalysts which increase the rate of reaction are called……….. Catalysts.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Concept of a Catalyst:**
- A catalyst is a substance that alters the rate of a chemical reaction without being consumed in the process. It can either increase or decrease the rate of reaction.

2. **Identifying Types of Catalysts:**
- Catalysts that increase the rate of a reaction are specifically known as positive catalysts.
- Conversely, catalysts that decrease the rate of a reaction are referred to as negative catalysts.
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