`16. A` have `->` has
`17. B` has you learned `->` have you learned
`18. B` whom `->` who
`19. B` badder `->` worse
`20. B` they study `->` they would study
`21. C` which book `->` whose book
`22. B` who house `->` whose house
`23. C` will reduce `->` should reduce
@ `Ly`