A student used a microscope to measure the length of a structure. The magnification was $\times 250$. The image size of the structure measured $5.00\ \text{mm}$. What was the true length of the structure?
- A$1.25 \times 10^{3}\ \text{mm}$
- B$1.25 \times 10^{3}\ \mu\text{m}$
- C$2.00 \times 10^{1}\ \mu\text{m}$
- D$2.00 \times 10^{-5}\ \mu\text{m}$