Read the following statements regarding evolution (A-D)-
A. Whales, bats, cheetah, and humans (all mammals) share similarities in the pattern of bones of forelimbs.
B. The diversity of life forms on earth has been changing over millions of years.
C. About 65 million years ago the dinosaurs suddenly disappeared from the earth.
D. A single-step large mutation is called speciation and explained by Herbert Spencer.
How many statements from the above is/are correct ?

Options

A. Four
B. Three
C. Two
D. One

Answer

To determine how many statements regarding evolution are correct, we will analyze each statement one by one.

### Step 1: Analyze Statement A
**Statement A:** Whales, bats, cheetah, and humans (all mammals) share similarities in the pattern of bones of forelimbs.

- **Analysis:** This statement is correct. The forelimbs of these mammals exhibit homologous structures, meaning they have a similar underlying bone structure despite serving different functions. This is a key concept in evolutionary biology that supports the idea of common ancestry.

### Step 2: Analyze Statement B
**Statement B:** The diversity of life forms on earth has been changing over millions of years.

- **Analysis:** This statement is also correct. Evolution is a gradual process that occurs over long periods of time, leading to the diversification of species. The fossil record and genetic studies provide evidence for this ongoing change in biodiversity.

### Step 3: Analyze Statement C
**Statement C:** About 65 million years ago, the dinosaurs suddenly disappeared from the earth.

- **Analysis:** This statement is correct. The mass extinction event that occurred around 65 million years ago, often attributed to an asteroid impact, led to the sudden disappearance of the dinosaurs and many other species.

### Step 4: Analyze Statement D
**Statement D:** A single-step large mutation is called speciation and explained by Herbert Spencer.

- **Analysis:** This statement is incorrect. Speciation is not defined as a single-step large mutation; rather, it is the process by which new species arise, often through gradual changes over time. The concept of large mutations leading to speciation is known as "saltation," and it is not attributed to Herbert Spencer but rather to other evolutionary theorists.

### Conclusion
- **Correct Statements:** A, B, and C are correct.
- **Incorrect Statement:** D is incorrect.

### Final Answer
Out of the four statements, three are correct.