Pelvic bone became rudimentary in which animal?

Options

A. Human
B. Ostrich
C. Whale
D. Placental mammals

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which animal has a rudimentary pelvic bone. The term "rudimentary" refers to a structure that has lost its original function through evolution.

2. **Identifying the Options**: The options provided are:
- A) Human
- B) Ostrich
- C) Whale
- D) Placental mammal

3. **Analyzing Each Option**:
- **Human**: Humans have a functional pelvic bone that supports walking and other activities.
- **Ostrich**: Ostriches, being birds, have a pelvic bone that is adapted for flight and bipedal movement, not rudimentary.
- **Whale**: Whales are aquatic mammals that have a pelvic bone that is reduced and serves no significant function in locomotion. This is an evolutionary remnant from their land-dwelling ancestors.
- **Placental Mammal**: This is a broad category that includes many animals, most of which have functional pelvic bones.

4. **Conclusion**: Based on the analysis, the animal with a rudimentary pelvic bone is the **whale**.

5. **Final Answer**: The pelvic bone became rudimentary in the **whale**.

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