The order of a reaction rarely exceeds ...........

Explanation

To solve the question, "The order of a reaction rarely exceeds ...........", we will analyze the factors affecting the order of a reaction and the probabilities involved in molecular collisions.

### Step-by-Step Solution:

1. **Understanding Reaction Order**:
- The order of a reaction is defined by the sum of the powers of the concentration terms in the rate law expression. It indicates how the rate of reaction depends on the concentration of reactants.

2. **Factors Influencing Reaction Order**:
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