The correct option is D Equinox is characterised by an equal duration of day and night.
During an equinox, the duration of the day is equal to the duration of the night. It occurs twice each year: 21 March and 23 September. Northern hemisphere and southern hemisphere experience opposite seasons at the same time of the year. So, when it is winter solstice in the northern hemisphere, it is summer solstice in the southern hemisphere. The shortest day in the northern hemisphere is on 22 December i.e., the day of the winter solstice.