Question

Uncle Mark bought a .........car last week.

1- 5-years-old.   2-  5-year-old.    3- 5-years'-old.   4- 5-year's-old

What is the correct answer and would you mind informing me the structure , please?

Answer 1

2-5 five year old is the correct answer as the whole phrase is /behaves like an adjective. Adjectives don't take the - s plural suffix.

Answer 2

2-  5-year-old

Answer 3

years-old