Many students have a hard time combining sentences. This activity helps them think about and discuss the reasons that the distractors are incorrect. Maybe they are too “wordy” (this is a useful term to teach children). Sometimes, an incorrect conjunction is used or the sentence parts are not in a logical order.
You can use this as a whole group activity to start (just do the first couple with the kids, discussing and making notes as you go). Once they have the hang of it, use it in a station or for work with partners. I would not suggest they do this independently, as you want them to discuss what makes one answer choice better than another.
You could also have them work on it with partners, then come together as a group to discuss their answers and justifications.