Answer:
1. A verb and a subject must both be plural or singular.
2. Perfect tense is used to indicate a completed action or condition. Continuous tense is used to indicate an action that is, was, or will be in progress at a certain time.
3. Auxiliary verbs are sometimes refereed to as helping verbs because they help form the various tenses, moods, and voices of other verbs.
4. Most infinitives will begin with the word to.
