Explanation: A sentence fragment is a group of words that look like a sentence but doesn´t posses a subject or the subject it´s not clear at all.
Also, the complement of the sentence marks that something happened with the subject, but we´re not sure of it. So it can´t considered as a sentence because there´s a part of it that it´s blurred.
Try to think of a disagreement or agreement you've EVER had with a family member. Even if you are exaggeration or making a bit of it up I believe it to be fine. Write about something simple like disagreement over the last cookie or bed time.
