Here's why:
* Subject-verb agreement: "Is" is singular, while "are" is plural. They cannot be used together.
* Missing a subject: A complete sentence needs a subject (who or what is doing the action) and a verb (the action). "Is are" only has a verb.
To make it a complete sentence, you need to provide a subject and correct the verb agreement:
* Example: "They are happy." (Subject: "They", Verb: "are")