What is the ultimate source of energy for all living beings ?

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the ultimate source of energy for all living beings. To answer this, we need to identify the primary source of energy that sustains life on Earth.

2. **Identifying the Process**: The key process to understand is photosynthesis. This process is crucial for converting energy from one form to another, specifically for plants and other photosynthetic organisms.

3. **Role of the Sun**: The Sun is the ultimate source of energy. It provides radiant energy in the form of sunlight, which is essential for photosynthesis.

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