REASON: the other options are possessive adjective for plural nouns. But since “tante” is singular,you have to use the singular possessive adjective which is “leur.” Thus choice B is the right answer.
The sentence below is using an incorrect possessive adjective. Correct the sentence with the right possessive adjective.
Leur tante est jolie. tante = féminin/ singulier jolie : féminin/singulier