Option 1: -40°

In this option, both thermometers would read the same temperature. This is because -40 degrees Fahrenheit is equal to -40 degrees Celsius. According to the Fahrenheit to Celsius conversion formula, to convert Fahrenheit to Celsius, we subtract 32 from the Fahrenheit temperature and then multiply it by 5/9. When we apply this formula to -40°F, we get -40°C. Therefore, both thermometers read -40°.

Option 2: 0°

In this option, the thermometers would not read the same temperature. 0 degrees Fahrenheit is equal to -17.8 degrees Celsius. Therefore, at 0 degrees Fahrenheit, the Celsius thermometer would read -17.8 degrees Celsius.

Option 3: -273°

In this option, the thermometers would not read the same temperature. -273 degrees Fahrenheit is equal to -169.4 degrees Celsius. Therefore, at -273 degrees Fahrenheit, the Celsius thermometer would read -169.4 degrees Celsius.

Option 4: 100°

In this option, the thermometers would not read the same temperature. 100 degrees Fahrenheit is equal to 37.8 degrees Celsius. Therefore, at 100 degrees Fahrenheit, the Celsius thermometer would read