Name the absorbing material used to control the reaction rate of neutrons in a nuclear reactor.

Explanation

To answer the question about the absorbing material used to control the reaction rate of neutrons in a nuclear reactor, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Role of Neutrons in a Nuclear Reactor:**
- In a nuclear reactor, neutrons play a crucial role in sustaining a nuclear chain reaction. When a neutron collides with a fissile nucleus (like Uranium-235), it can cause the nucleus to split, releasing energy and more neutrons.

2. **Identifying the Need for Control:**
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