State one main function of each of the following:
(i) Cerebellum, (ii) Iris, (iii) Eustachian tube

Explanation

To answer the question regarding the main functions of the cerebellum, iris, and Eustachian tube, we can break it down step by step:

### Step-by-Step Solution:

1. **Cerebellum**:
- The cerebellum is a major structure located in the hindbrain, near the brain stem.
- Its primary function is to regulate motor movements. This includes coordinating voluntary movements, maintaining balance, and ensuring proper posture.
- **Main Function**: Regulating motor movements and coordination.
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