A complex sentence is one containing a principal clause and one or more subordinate clauses.
No. 20 is a simple sentence, with a complex sentence in parenthesis.
The independent (main) clause of a complex sentence may be compound.
A dependent clause in a complex sentence may also be an adjective clause.
In bringing the truths within the comprehension of children, the author has made sparing use of the complex sentence.
When you add a dependent clause you have a complex sentence.
The third kind of clause which we may use in a complex sentence is the adverb clause.
This is a complex sentence because it contains dependent clauses.
The complex sentence has only one main clause and one or more dependent clauses.
A complex sentence consists of two or more clauses, one of which is independent and the rest subordinate.
A sentence that contains one main clause or independent clause and at least one subordinate clause or dependent clause: “Although I am tired (subordinate clause), I want to go to the midnight movie (main clause).” (See subordination; compare compound sentence, compound-complex sentence, and simple sentence.)