The statement which is a sentence is: 5. How are you?
A sentence can be defined as a group of words that comprises both a predicate, object and a subject, which are used to convey a logical information and express a complete thought.
"How are you?" is an example of a sentence because it contains a contains an object, which is the person being asked a question by the subject.
Also, "How are you?" is a sentence that conveys a logical information and expresses a complete thought.
Find more information on subject and predicate here: https://brainly.com/question/20784856