Answer:
A complex sentence
Explanation:
A complex sentence is a type of sentence made up of one independent clause (a clause that expresses a complete thought) and at least one dependent clause (a clause that can not stand alone as a sentence because it does not express a complete thought).
In this type of sentence, the dependent clause is often introduced by a coordinating conjunction such as <em>when, after, while, because, if </em>and<em> until</em>, which also indicate the subordination of the clause to the independent clause.
Here are some examples (independent clauses are underlined and dependent clauses are not underlined):
<em>When Mike left the room, </em><u><em>Vanessa started crying.</em></u>
<u><em>I usually tell my child stories at night</em></u><em> until he falls asleep.</em>