A mixture of radioactive substances gives off three types of radiations :
Name the radiation which travels with the speed of light

Explanation

To solve the question, we need to identify the type of radiation emitted by radioactive substances that travels at the speed of light.

### Step-by-Step Solution:

1. **Understanding Radioactive Radiation**:
- Radioactive substances emit three main types of radiation: alpha particles, beta particles, and gamma rays.

2. **Identifying the Speed of Each Radiation**:
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