A subordinate clause is a dependent clause that is connected to the main sentence using subordinating conjunctions such as: because, if, once, after, before, although, and etc. This clause adds more information or ideas to the main sentence. In the sentence given, the subordinate clause is, option A. although other subspecies are also threatened.
Without knowing the context of this question I would say a lot of horror films come from real life experiences exaggerated and from dreams of the writer.
Explanation: Read about horror writers and their influences.