The correct answer is: $-4\text{ °F}$
Explanation
To convert Celsius to Fahrenheit use the formula $F = C \times \frac{9}{5} + 32$.
Steps:
- Formula: $$F = C \times \frac{9}{5} + 32$$
- Substitute $C = -20$: $$F = -20 \times \frac{9}{5} + 32$$
- Compute: $$F = -36 + 32 = -4\text{ °F}$$
Therefore, $-20^\circ\text{C}$ equals $-4\text{ °F}$.