The correct response is: It is a dependent clause.
Explanation:
A sentence fragment is an incomplete sentence that cannot stand alone because it does not express a complete thought. In this case, the phrase "Although there was not much hope she would ever understand the reasons behind my actions" begins with "Although," which indicates that it is introducing a dependent clause. A dependent clause cannot stand alone as a complete sentence because it relies on an independent clause to provide full context and meaning. To make it a complete sentence, it would need to be connected to an independent clause.
For example: "Although there was not much hope she would ever understand the reasons behind my actions, I decided to explain anyway."