Of the group of words presented as options, the sentence fragment of them would be A. When we stopped by the garden.
Sentence fragments, or just fragments, are much like dependent clauses. They aren't able to stand on their own, but are sometimes depicted as lone sentences. This is only when they are partnered with a complete sentence before they are presented. This would then present that the sentence fragment is clearly referring to the previous thought presented to the sentence prior to the fragment.
B. stopping by the garden, we saw that the flowers were in bloom. this sentence presents a complete thought and is a complete sentence.
C. We stopped; she didn't. on the other hand also presents clear and complete thought.
D. Stop by the garden. is an acceptable form of sentence that is under the classification of a command.
