The answer to your question would be that the option that is an example of a complex sentence is the following one: The democratic process is successful because people have the right to vote (B).
Explanation:
A complex sentence has at least one independent clause (see 1) and one dependent clause (see 2). The difference between an independent clause and a dependent one is that the former can stand alone as a sentence because it represents a complete thought.
Alright for everyone whos not capable of getting this answer right, is - The democratic proccess is successful because people have the right to vote - apex