HOW CAN WE PREVENT ...

81. - 400 CAU TRAC NGHIEM ON TAP ANH 9 4OO CAU TRAC NGHIEM ON TAP L9
400 CAU TRAC NGHIEM ON TAP ANH 9 4OO CAU TRAC NGHIEM ON TAP L9

81.

How can we prevent ...?

a.

litter b. pollute c. polhited d. littering