Sometimes, it needs a verb; sometimes it needs a subject.
I'm not sure if this is what you need, but an example of a sentence fragment containing the word tree is below. The bird in the tree. (This is a sentence fragment and not a complete sentence because there is no verb (action word).
Ate the cake is a fragment because there is no subject. To be a complete sentence, it must have a subject and a verb. You would need to change it to, I ate the cake, or She ate the cake, or so on.
It is a fragment as there is no subject. Even if you use it as an answer to a question, it is still a fragment, i.e. "Where is the desk? In the middle of the office." For it to be a complete sentence as an answer to a question, you would need to change the sentence to "It's" or "the desk", "is in the middle of the office."
Do you work? is a complete sentence; it is not a sentence fragment.
"She wave." is fragment but "She waves" is a sentence.
fragment
D Here is. This is a fragment sentence because there is no subject in the clause.
Fragment.
Fragment
sentence fragment
It is a sentence fragment
Make each fragment into a complete sentence.