求大神做英语定语从句六题,18.This is thevery letter ____came last night.A

求大神做英语定语从句六题,
18.This is the
very letter ____came last night.
A.who B.
which C.that D.as
19.I know only a
little about this matter; you may ask ____ knows better than I.
A.whoever B.whomever C.
anyone D.the one
20.This is the
school ____ we visited three days ago.
A.where B./ C.
when D.what
21.This is the
factory ____ we worked a year ago.
A.where B.that C.
which D.on which
22.Nearby were
two canoes ____ they had come to the island.
A.which B.in which C.
that D./
23.Jack is
pleased with ____ you have given him and all ____ you have told him.
A.that,what B.what,that C.
which,what D.that,which