HE IS COLLECTING STAMPS AND HE HAS A VALUABLE ... OF STAMPS.A. NUM...

19. - 3500 CAU TRAC NGHIEM ON TAP AV THCS
3500 CAU TRAC NGHIEM ON TAP AV THCS

19. He is collecting stamps and he has a valuable ... of stamps.

a. number

b. collection

c. packet

d. pile

 b