Concept:The summer solstice is the day when the Northern Hemisphere receives the longest period of daylight because the Sun is highest in the sky at noon.Explanation:Around June 21, the Northern Hemisphere tilts directly toward the Sun.The Sun is overhead at the Tropic of Cancer, at approximately 23.5∘ N.This causes the longest day and shortest night of the year in the Northern Hemisphere.This event is called the summer solstice.On the same date, the Southern Hemisphere experiences its winter solstice.Answer:C. June 21