Step 1: Concept Overview:
The question seeks identification of an egg-laying (oviparous) mammal. While most mammals are viviparous (live birth), monotremes represent an exception as oviparous mammals.
Step 2: Detailed Explanation:
- Mammals (Class Mammalia) are categorized into three groups based on their reproductive methods:
1. Monotremes: The only egg-laying mammals. Examples: platypus and echidnas.
2. Marsupials: Viviparous mammals giving birth to underdeveloped young that mature in a pouch. Examples: kangaroos ({Macropus}), koalas, and opossums.
3. Placental Mammals (Eutherians): Viviparous mammals with full fetal development inside the mother's uterus via a placenta. This is the largest group, including bats ({Pteropus}), rats ({Rattus}), and humans.
- Option Analysis:
- (A) {Macropus}: Kangaroo (marsupial).
- (B) {Pteropus}: Flying fox (placental mammal).
- (C) {Rattus}: Rat (placental mammal).
- (D) {Platypus}: Monotreme; an egg-laying mammal.
Step 3: Conclusion:
The platypus is the only oviparous mammal presented. Therefore, (D) is the correct answer.