How can surrounding tones be used effectively to make a lit area appear brighter?

Correct answer: Place relatively darker tones around it to create controlled contrast

The governing concept is tonal contrast: the apparent brightness of a patch depends partly on the values around it. If relatively darker tones are placed beside the lit area, the difference in value becomes clearer, so the light area appears brighter without changing its actual pigment. The same light tone would reduce contrast, while blurring or whitening the whole picture would weaken form and emphasis. Therefore, option C is correct.