Their shoes: mis zapatos sus zapatos tus zapatos nuestros zapatos

Their shoes = Sus zapatos

Explanation:

Because their means "sus"  

And "sus" comes from "ellos", and "ellos" means "they".

Remember: "Sus" is a Possessive pronoun for use when are "ellos (They)"

lack of land area is one of the things not mentioned that has contributed to the poor transportation and communication systems in nicaragua.