$ Unicellular eukaryotes are the simplest organisms.
! Prokaryotes have the mitochondria whereas eukaryotes are without mitochondria.

Options

A. If both As and R are correct and R is correct explanation of As
B. If both As and R are correct but R is not correct explanation of As
C. If As is correct, R is wrong
D. If both As and R are wrong.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that "unicellular eukaryotes are the simplest organisms."
- **Analysis**: Unicellular eukaryotes are indeed single-celled organisms, but they are not the simplest. The simplest organisms are actually unicellular prokaryotes, which lack a defined nucleus and membrane-bound organelles.

2. **Understanding the Reason**: The reason states that "prokaryotes have mitochondria whereas eukaryotes are without mitochondria."
- **Analysis**: This statement is incorrect. Prokaryotes do not have mitochondria or any other membrane-bound organelles. Mitochondria are found in eukaryotic cells, not in prokaryotic cells.

3. **Conclusion**: Since both the assertion and the reason are incorrect, we can conclude that the correct answer is that both statements are false.

4. **Final Answer**: Therefore, the correct option is that both the assertion and the reason are incorrect.