What is the principal nitrogenous waste product in (i) fish, and (ii) birds?

Explanation

To answer the question regarding the principal nitrogenous waste product in fish and birds, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding Nitrogenous Waste Products**:
- Nitrogenous wastes are the byproducts of protein metabolism and are primarily excreted in three forms: ammonia, urea, and uric acid.

2. **Nitrogenous Waste in Fish**:
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