In a diagram, the diameter of a red blood cell was measured to be $2.5\ \text{cm}$. Its true diameter was $7\ \mu\text{m}$. Which calculation would produce the correct magnification of the red blood cell shown in the diagram?
- A$\frac{7}{25000}$
- B$\frac{2500}{7}$
- C$\frac{25000}{7}$
- D$\frac{25000}{7000}$