Answer:1. whomever (objective)
Jack hits the ball to whomever has a mitt. (Indirect object)
2. whoever (nominative)
Whoever has a glove can play.
3. who (nominative)
Who is at the door?
4. whom (objective)
Whom did you see when you opened the door?
5. which (nominative/objective)
Which is my slice of pie? (Nominative). The choice boiled down to which came first. (Objective)
6. that (nominative/objective)
That is never an option. (Nominative). I don't think much of that. (Objective)
