What element is essential in forming a compound-complex sentence?

A compound-complex sentence is defined by its structure, which must contain at least two independent clauses and at least one dependent clause. The presence of at least one dependent clause is essential because it provides additional information or context to the independent clauses, creating a more complex thought.

In this context, the correct answer highlights the necessity of including a dependent clause in a compound-complex sentence, which distinguishes it from simpler sentence types. By integrating dependent clauses, writers can elaborate on ideas and link concepts in ways that enrich the overall meaning of the sentences. This complexity allows for a more nuanced expression of thoughts than if only independent clauses were used.

The other options do not encapsulate the full requirement of a compound-complex sentence. While multiple independent clauses are part of the structure, they are not sufficient on their own without the inclusion of a dependent clause. Thus, the element that is essential is indeed the presence of at least one dependent clause.