Change the active voice into passive in the following sentences: 1.acid rain and acid snow poison rivers and lakes too. 2.many countries produce acid rain. 3.people can clean the smoke from factories and pover stations,but it is too expensive.

1.Rivers and lakes are poisoned by acid rain and acid snow.
2.Acid rain is produced by many countries.
3.The smoke from factories and power stations can be cleaned by people,but it is too expensive.