Question

select the word that means the length of time something lasts. a year on earth consists of 365 days, more or less. but on other planets, a year can be much shorter or longer. the duration of a planets year is measured by the time it takes to complete a full orbit around the sun. the closest planet to the sun, mercury, takes a quick 88 earth days to orbit the sun. at the other end of our solar system, neptunes year is 60,182 earth days, or 164.8 earth years, long.

Explanation:

The question asks for the word that means "the length of time something lasts". Looking through the provided text, the word "duration" is explicitly used to describe the length of a planet's year (the time it takes to orbit the sun), which matches the defined meaning.

Answer:

duration