Answer:
D. Before politicians can make any progress, they need to be willing to compromise.
Explanation:
Before is a subordinating conjunction, so the clause it is included in cannot stand alone and needs to join an independent clause in order to make sense. In this case, the subordinating clause "Before politicians can make any progress" is linked to the independent clause "they need to be willing to compromise" to form a complex sentence with a comma separating the clauses.
