Biology 9700/12 — February/March 2023

The photomicrograph shows cells from a human blood smear.

Which calculation shows a correct method to calculate the actual diameter of the neutrophil shown in the photomicrograph in micrometres ($\mu\text{m}$)?

Options

A   $\frac{\text{length of line PQ in mm} \times 1000}{\text{magnification of photomicrograph}}$
B   $\frac{\text{length of line PQ in mm} \times 10\,000}{\text{magnification of photomicrograph}}$
C   $\frac{\text{magnification of photomicrograph}}{\text{length of line PQ in mm} \times 1000}$
D   $\frac{\text{magnification of photomicrograph}}{\text{length of line PQ in mm} \times 10\,000}$