HE IS COLLECTING COINS AND HE HAS A VALUABLE ... OF RARE COINS.A....

21. - 3500 CAU TRAC NGHIEM ON TAP AV THCS
3500 CAU TRAC NGHIEM ON TAP AV THCS

21. He is collecting coins and he has a valuable ... of rare coins.

a. number

b. collection

c. packet

d. pile

 b