Question

if the wrong word is used below, change it. if there is no error, click \submit answer.\ luisa rivera offered the chemists a coupon for a free steak, but their all vegetarians.

Explanation:

The word "their" is a possessive pronoun. Here, we need a subject - pronoun "they're" (a contraction of "they are") to indicate that the chemists are vegetarians.

Answer:

they're