B. You are right!! It is a conplex sentence so you can slot the middle part of the sentence (between the two commas) in and out of the sentence: My cousin volunteers at the local clinic every weekend would be the base sentence but sentence B is a conplex sentence! Hope that helped your understanding.
I would start with simple definitions to teach them, the words would depend on the grade they are in, then the words would get harder as we make progress.
Explanation: Hope this helps:).......if not sorry for wasting your time:)
