UNIT 7CHOOSE A,B,C, OR D TO COMPLETE THE FOLLOWING SENTENCES

37. - BAI TAP ON TAP KIEM TRA TRAC NGHIEM ANH9 CA NAM
BAI TAP ON TAP KIEM TRA TRAC NGHIEM ANH9 CA NAM
37. If we go ……littering, the environment will become seriously pollutedIn out to on