Concept:The summer solstice in the southern hemisphere occurs when the Sun is directly overhead the Tropic of Capricorn, causing the longest day of the year there.Explanation:Around 22nd December, the Sun’s rays fall vertically on the Tropic of Capricorn at 23.5∘ S.At this time, the southern hemisphere receives maximum solar energy.This results in the longest day and shortest night, which marks the summer solstice for that hemisphere.Therefore, the correct date from the given options is 22nd December.Answer:B. 22nd December