Why is earth called closed system with reference to materials ?

Explanation

### Step-by-Step Solution:

1. **Understanding System Types**:
- There are three types of systems: open, closed, and isolated.
- An open system allows both matter and energy to flow in and out.
- A closed system allows energy to flow in and out, but matter cannot enter or leave.
- An isolated system does not allow either matter or energy to enter or leave.

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