Answer:
c. Solstice describes days when sun's rays directly hit Tropic of Cancer and Tropic of Capricorn.
Step-by-step explanation:
The solstices occur due to the declination of the Earth's orbital movement around the sun. During this declination, the axial tilt is 23.5°. Furthermore, solstice's occurrence is during time the sun's direction is overhead the moon.
In Northern hemisphere, the declination is towards Tropic of Cancer with the axial tilt of 23.5°N. It occurs on June 20 & 22 while in the south the normal period of occurrence is between December 20 and December 23. In the south, the solar declination hits Tropic of Capricorn at 23.5°S.