The photomicrograph displays a plant cell. The length of line XY is $90\ \text{mm}$. The actual length of the cell is $30\ \mu\text{m}$. What is the magnification of the photomicrograph?
- A$\times 300$
- B$\times 3000$
- C$\times 33\,000$
- D$\times 330\,000$