3. Complex :A complex sentence has an independent clause joined by one or more dependent clauses. It always uses a subordinator such as because, since, after, although, or when or a relative pronoun such as that, who, or which to connect the clause together.
a. We visited the museum before it closed.
b. She left before the party was over.
c. After we had learned about grammar, we understood all the
English grammatical.
d. While we were playing the violin, our mother came in.