Internal fertilization is found in all

Options

A. reptiles, birds, mammals
B. insects, annelies, echinoderms
C. sponges, flatworm, protochordates
D. fishes, amphibians, coelenterates

Answer

**Step-by-Step Solution:**

1. **Understanding Internal Fertilization:**
- Internal fertilization occurs when the male and female gametes fuse inside the female's body. This is in contrast to external fertilization, where the fusion occurs outside the body.

2. **Analyzing the Options:**
- The question provides several groups of animals, and we need to determine which of these groups exhibits internal fertilization.

3. **Option A: Reptiles, Birds, and Mammals:**
- All three groups (reptiles, birds, and mammals) are known to exhibit internal fertilization.
- Reptiles lay eggs that are fertilized inside the female body.
- Birds also fertilize their eggs internally before laying them.
- Mammals give birth to live young, with fertilization occurring internally.

4. **Option B: Insects, Annelids, and Echinoderms:**
- Insects and annelids generally exhibit internal fertilization, but echinoderms (like starfish) typically reproduce via external fertilization. Hence, this option is incorrect.

5. **Option C: Sponges, Flatworms, and Protocordates:**
- Sponges (phylum Porifera) and flatworms (phylum Platyhelminthes) usually reproduce via external fertilization. Protocordates also do not typically exhibit internal fertilization. Therefore, this option is incorrect.

6. **Option D: Fishes, Amphibians, and Cylindrids:**
- Most bony fishes and amphibians (like frogs) reproduce through external fertilization. Thus, this option is also incorrect.

7. **Conclusion:**
- The only correct option that includes animals that exhibit internal fertilization is **Option A: Reptiles, Birds, and Mammals**.

**Final Answer:**
Internal fertilization is found in all **Reptiles, Birds, and Mammals** (Option A).

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