A temperature dropped from 15°C to -5°C. What was the total change in temperature?

The initial temperature ($T_{\text{initial}}$) is $15^\circ\text{C}$.
The final temperature ($T_{\text{final}}$) is $-5^\circ\text{C}$.

The total change in temperature ($\Delta T$) is found by subtracting the initial temperature from the final temperature.

The total change in temperature is $-20^\circ\text{C}$.

The final answer is $\text{C. } -20^\circ\text{C}$.