A catalyst remains unchanged at the end of the reaction regarding:

Options

A. Mass
B. Physical state
C. Physical state and chemical composition
D. Mass and chemical composition

Explanation

To answer the question, "A catalyst remains unchanged at the end of the reaction regarding:", we can break down the information provided in the video transcript step by step.

### Step-by-Step Solution:

1. **Definition of a Catalyst**:
- A catalyst is a substance that increases the rate of a chemical reaction without undergoing any permanent chemical change itself.

2. **Unchanged Properties**:
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