Answer:
The correct option is C. complicated relationships.
Step-by-step explanation:
There are several forms of sentences you used in writing; simple sentences, compound sentences, and finally, complex and compound-complex sentences. Being the last type the longest since they combine two different types of sentences into one; a compound sentence (which joins two or more independent clauses) with a complex sentence (which joins an independent clause and one or more dependent clauses).
Bearing the above in mind, it could be said that compound-complex sentences are typically used to express complicated relationships.