**Step-by-Step Solution:**
1. **Understanding the Function of Lungs in Frogs:**
- Frogs have lungs that are primarily used for respiration, especially when they are on land. This is an important aspect to consider when identifying the characteristics of their lungs.
2. **Identifying the Structure of Frog Lungs:**
- Frog lungs are two in number and are described as delicate structures. They are not solid but rather have a specific structure that allows for gas exchange.
3. **Analyzing the Properties of Frog Lungs:**
- The lungs are elastic, which means they can expand and contract. This elasticity is crucial for their function in respiration.
- The color of the lungs is typically pinkish, which is a characteristic feature of many living tissues due to the presence of blood vessels.
4. **Shape and Composition of Frog Lungs:**
- The lungs are described as being sack-like and not perfectly circular. They are thin-walled and hollow, which allows for efficient gas exchange.
5. **Evaluating the Options:**
- The options provided are:
a) Distensible, pinkish, sack-like
b) Distensible, pinkish, and solid
c) Distensible, pinkish, and spongy
d) Distensible, rosy, and spongy
- Since we established that frog lungs are distensible, pinkish, and sack-like, we can eliminate options that do not match these characteristics.
6. **Conclusion:**
- The only correct option that accurately describes the lungs in frogs is **distensible, pinkish, and sack-like**.
**Final Answer:**
- The correct description of lungs in frogs is: **Distensible, pinkish, and sack-like.**
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