Which sentence uses correct subject-verb agreement?

the alligators slips quietly into the water.
the alligators slipping quietly into the water.
the alligator slipping quietly into the water.
the alligator slipped quietly into the water.

Match the definition to the term. 1. pronouns or verbs used to show the person speaking, the person spoken to person 2. a form of noun, pronoun, or adjective used to show its relation to other words gender 3. the grouping of nouns into the classes masculine, feminine, and neuter case 4. an inflection or word form that shows whether one or more than one is meant number 5. pronouns that show by their form personal pronouns