What advantage do the fuel cells have over primary and secondary batteries?

Explanation

### Step-by-Step Solution:

1. **Understanding Primary Batteries:**
- Primary batteries are designed to be used until the reactants are exhausted. Once the chemical reactions have occurred and the reactants are consumed, these batteries cannot be recharged or reused.
- **Example:** Zinc-carbon battery.

2. **Understanding Secondary Batteries:**
- Secondary batteries, unlike primary batteries, can be recharged. However, the recharging process can be time-consuming, which may limit their practicality in certain situations.
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