Assertion : The alimentary canal of the frog is short
Reason : Frogs are carnivores.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false

Explanation

### Step-by-Step Solution

1. **Understanding the Assertion**: The assertion states that "The alimentary canal of the frog is short." This means that the digestive system of the frog, which includes the mouth, esophagus, stomach, intestines, and anus, is relatively shorter compared to other animals.

2. **Understanding the Reason**: The reason provided is "Frogs are carnivores." This indicates that frogs primarily eat other animals, such as small invertebrates, rather than plant material.

3. **Analyzing the Relationship**:
- Carnivores typically have shorter alimentary canals compared to herbivores. This is because animal tissues are easier to digest than plant materials, which often contain cellulose that requires more time and a longer digestive tract to break down.
- Frogs, being carnivorous, consume a diet that is rich in proteins and fats, which are more easily digestible.

4. **Conclusion**: Since the assertion (the alimentary canal of the frog is short) is true and the reason (frogs are carnivores) correctly explains why the assertion is true, we conclude that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

5. **Final Answer**: The correct option is A: "If both assertion and reason are true, the reason is the correct explanation of the assertion."