Try to recycle things and we will save natural resources.

=> If we ...

(a)  

Lucie doesn't swim as fast as her sister.

=> Lucie's sister swims ...

(a)  

I'm sorry I can't play the piano.

=> I wish ...

(a)  

"May we use the computer now?", they asked the teacher.

=> They asked the teacher ...

(a)  

The exercise was so difficult that we couldn't do it.

=> It was ...

(a)  

People celebrate Passover in Israel in late March or early April.

=> Passover ...

(a)