Different cells have different sizes. Arrange the following cells in an ascending of their size and select the correct option.
(i) Mycoplasma (ii) Ostrich egg
(iii) Human RBCs (iv) Bacteria

Options

A. a) `(i) rarr (iv) rarr (iii) rarr (ii)`
B. b) `(i) rarr (iii) rarr (iv) rarr (ii)`
C. c) `(ii) rarr (i) rarr (iii) rarr (iv)`
D. d) `(iii) rarr (ii) rarr (i) rarr (iv)`

Explanation

To arrange the given cells in ascending order of their size, we need to first identify the size of each cell type:

1. **Mycoplasma**: This is known to be one of the smallest cells, with a size ranging from approximately **0.1 to 0.5 micrometers**.

2. **Bacteria**: Bacterial cells typically measure around **3 to 5 micrometers** in length.

3. **Human RBCs (Red Blood Cells)**: Human RBCs have a diameter of about **6 to 8 micrometers**.

4. **Ostrich Egg**: The ostrich egg is the largest cell, which can be several centimeters in size (specifically, around **15 centimeters** in diameter).

Now, we can arrange these cells in ascending order based on their sizes:

- **Mycoplasma** (0.1 to 0.5 micrometers)
- **Bacteria** (3 to 5 micrometers)
- **Human RBCs** (6 to 8 micrometers)
- **Ostrich Egg** (largest cell, several centimeters)

Thus, the ascending order of the cells by size is:

1. Mycoplasma (smallest)
2. Bacteria
3. Human RBCs
4. Ostrich Egg (largest)

The correct sequence is **1 (Mycoplasma), 4 (Bacteria), 3 (Human RBCs), 2 (Ostrich Egg)**.

### Final Answer:
**1, 4, 3, 2**