On 21 st June, the Sun

The correct answer is A. On 21 June the Sun is at its maximum northern declination of about +23.5°, which is the summer solstice in the Northern Hemisphere. The Arctic Circle at 66.5°N lies exactly at the edge of the zone where the Sun stays up for a full 24 hours around the solstice, so the Sun does not set there on that day.

• B is wrong: The Antarctic Circle (66.5°S) is in the middle of polar night on 21 June. The Sun stays below the horizon there, not above it.
• C is wrong: The Sun is overhead at the Equator at noon only near the equinoxes, around 21 March and 23 September.
• D is wrong: On 21 June the vertical Sun lies on the Tropic of Cancer (23.5°N). The Tropic of Capricorn gets a vertical Sun around 22 December.

The core concept is the relation between the Earth's axial tilt of 23.5°, the solstices, and the polar day and night zones. This links directly to Mains GS-I geography questions on seasons, day length and insolation belts. Remember that the Arctic Circle is a limit, not a point where the Sun barely touches the horizon at noon.

Trap: Many candidates pick C or D by mixing up the equinox and solstice dates, or by assuming the Sun is overhead at the Tropic of Capricorn in June because it is the southern tropic.