Which corrects the incorrect pronoun or contraction in the sentence? They're sister is happy to babysit, so you mustn't worry about it. A. their B. mustnt C. there D. must'nt

A.) Their

Their sister is happy to babysit, so you mustn't worry about it.

Their is the 3rd person plural adjective. It is used to describe something or someone that belongs to them.

They're is a contraction of "they are" and it is most often followed by a present participle or a verb that ends with - ing.

A. their is the correct answer