$\text{1. If they are polluted, the rice plants will die.}$

$\text{2. I think we should get a plumber to check the pipes.}$

$\text{3. He is disappointed to hear his exam result.}$

$\text{4. The students are learning English in the room at present.}$

$\text{5. I suggested that Peter should study harder this semester.}$

$\text{6. I was a child since the song has been sung.}$

$\text{7. I want to meet the man who he is right now.}$

$\text{8. If we go on littering, the environment will become seriously polluted.}$

$\text{9. She doesn't miss any weather forecasts on TV.}$

$\text{10. I like my watch which I was given on my last birthday.}$

$\text{11. Easter at around happens the same time as Passover.}$

$\text{12. If he tried harder, Tuan would get better grades.}$