The correct answer is option 3: 6000°K.

The surface temperature of the Sun refers to the temperature at the outermost layer of the Sun, known as the photosphere. The photosphere is the layer where most of the Sun`s light is emitted, giving us the light and heat we receive on Earth.

The surface temperature of the Sun is incredibly hot, and it is estimated to be around 5,500 to 6,000 degrees Kelvin (°K). Kelvin is a unit of temperature where 0°K represents absolute zero, the point at which all molecular motion ceases. Therefore, a temperature of 6,000°K indicates an extremely high temperature.

Options 1 and 2 are lower than the correct answer and underestimate the actual surface temperature of the Sun. Option 4 overestimates the surface temperature. Therefore, the correct answer is option 3, 6000°K.

It`s important to note that the temperature of the Sun can vary in different layers and regions, with the core being much hotter than the surface. The surface temperature mentioned here is specifically referring to the photosphere.