Answer: Revolution
Explanation:
The Earth rotates about its axis in 23 hours 56 minutes i.e. in one day. The Earth revolves around the Sun in one year (365 and 6 hours). Axis is an imaginary line passing through the center of any body about which it rotates. Solstice is an event when Sun is passing over Tropic of Capricorn or Tropic of cancer.
Hence, the correct option is The earth completes one Revolution when it travels once around the sun.
