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? 1 a temperature increase of 1 degree fahrenheit is equivalent to a temperature increase of 5 9 degree celsius. 11 a temperature increase of 1 degree celsius is equivalent to a temperature increase of 1.8 degrees fahrenheit. 111 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