1.The students have discussed the pollution problems since last week.
=>the pollution problems have  been discussed since last week

2. Tom has seen this film before.
=>this film has been seen 

3. Mary has read the newspaper already.
=>the newspaper has been read 

1. The students has discussed the pollution problems since last week

-> The pollution problems have been discussed by the students since last week
2.Tom has seen this film before.
.->This film has been seen before
câu 3 mk ko biết làm
 

1.The students have discussed the pollution problems since last week.
-> The pollution problems have been discussed by the students since last week.
2. Tom has seen this film before.
-> this film has been seen by Tom before
3. Mary has read the newspaper already.
->The newspaper has been read already by Mary