Which of the following is a sentence fragment?

A sentence fragment is a group of words that looks like a sentence, but actually isn't a complete sentence. Sentence fragments are usually missing a subject or verb, or they do not express a complete thought. While it may be punctuated to look like a complete sentence, a fragment cannot stand on its own

Explanation:

16.) true

17.) true

18.) no information in the text

19.) false

20.) no information in the text

if its apex this should be the correct answer

war information to be released publicly must first be deemed useless to the enemy