The equation above shows how temperature $f$, measured in degrees fahrenheit, relates to a temperature $c$, measured in degrees celsius. based on the equation, which of the following must be true? a temperature increase of 1 degree fahrenheit is equivalent to a temperature increase of $5/9$ degree celsius. a temperature increase of 1 degree celsius is equivalent to a temperature increase of 1.8 degrees fahrenheit. a temperature increase of $5/9$ degree fahrenheit is equivalent to a temperature increase of 1 degree celsius. a) i only b) ii only c) iii only d) i and ii only