The correct answer is option 4: Sidereal year. The sidereal year is the time it takes for the Earth to complete one full orbit around the Sun with respect to the fixed stars. This means that it is the time required for the Earth to return to the same position in its orbit as seen from outside the solar system.
Option 1: Lunar year refers to the time it takes for the Moon to complete one orbit around the Earth, which is approximately 27.3 days. This is not the correct answer because it is specifically referring to the Moon`s orbit, not the Earth`s orbit.
Option 2: Solar year refers to the time it takes for the Earth to complete one orbit around the Sun with respect to the seasons. It is based on the position of the Sun in the sky and is approximately 365.24 days. Although this is related to the Earth`s orbit, it is not the correct answer as it is not specifically referring to the fixed stars.
Option 3: Tropical year refers to the time it takes for the Earth to complete one orbit around the Sun with respect to the seasons, specifically the position of the Sun at the vernal equinox. It is approximately 365.24 days, the same as the solar year. This