The correct answer is option 1: 6000 °C. The surface temperature of the sun is estimated to be around 6000 °C. This temperature is measured using various methods, including spectroscopy and the analysis of the sun`s black-body radiation. Spectroscopy involves studying the light emitted by the sun and analyzing its different wavelengths to determine the temperature. The sun`s black-body radiation refers to the energy it emits as heat due to its high temperature. Scientists have conducted extensive research and observations to arrive at the conclusion that the surface temperature of the sun is approximately 6000 °C. It is important to note that while this is the estimated surface temperature, the temperature at the core of the sun is much higher, reaching millions of degrees Celsius.