For a group of words to qualify as a sentence there are some necessary elements that must be present. A simple sentence for instance must contain a subject and a verb or predicate. The subject is the who, what or where of the sentence and the verb shows the action of the subject. www.superteacherworksheets.com/actionverbs.html has verb worksheets available that help you to identify action
. verbs, linking verbs, subject-verb agreement, verb tenses and more.