Answer:
Fragment.
Step-by-step explanation:
Sentence fragments are groups of words that seem like a sentence but do not make a complete sentence or complete a thought. They are like dependent clauses as they cannot stand on their own as a complete sentence.
The given groups of words "When I watched my mother baking bread" is a fragment as it does not complete the thought. It is also not a complete sentence, leaving the readers hanging for how the sentence might end.
Thus, the correct answer is a fragment.