Nitrogenous waste products are eliminated mainly as

Options

A. urea in tadpole and uric acid in adult frog
B. urea in adult frog and ammonia in tadpole
C. urea in tadpole as well as in adult frog
D. urea in tadpole and ammonia in adult frog

Answer

### Step-by-Step Solution:

1. **Understanding Nitrogenous Waste Products**:
- Nitrogenous waste products are substances that contain nitrogen and are produced as a result of protein metabolism. The main types of nitrogenous waste products are ammonia, urea, and uric acid.

2. **Identifying Nitrogenous Waste in Aquatic Organisms**:
- Ammonia is the primary nitrogenous waste product in aquatic organisms because it is highly soluble in water and can be easily excreted. Organisms that excrete ammonia are known as ammonotelic organisms.

3. **Tadpole Nitrogenous Waste**:
- Tadpoles are aquatic and primarily excrete ammonia as their nitrogenous waste. This is due to their aquatic environment, which allows for the dilution of ammonia in water.

4. **Identifying Nitrogenous Waste in Adult Frogs**:
- Adult frogs, being semi-terrestrial amphibians, primarily excrete urea. They are classified as ureotelic organisms. Urea is less toxic than ammonia and requires less water for excretion, making it suitable for terrestrial life.

5. **Analyzing the Options**:
- The question provides several options regarding the nitrogenous waste products of tadpoles and adult frogs:
- A) Urea in tadpole, uric acid in adult frog
- B) Urea in adult frog and ammonia in tadpole
- C) Urea in tadpole as well as in adult frog
- D) Urea in tadpole and ammonia in adult frog
- Based on our understanding, option B is correct: ammonia is excreted by tadpoles, and urea is excreted by adult frogs.

6. **Final Answer**:
- Therefore, the correct answer is **Option B: Urea in adult frog and ammonia in tadpole**.