Explanation:

Date during the year when the declination of the Sun is at 23.5° South of the equator. During the December solstice, locations in the Northern Hemisphere experience their shortest day. The December solstice is also the first day of winter in the Northern Hemisphere. Locations in the Southern Hemisphere have their longest day on the June solstice. This date also marks the first day of summer in the Southern Hemisphere.
 Key Facts
Declination: Location (latitude) on the Earth where the Sun on a particular day is directly overhead (90° from horizon) at solar noon. This location is somewhere between 23.5° North and 23.5° South depending on the time of the year. Hence option 1st is correct.