把下列句子变为被动语态或主动语态

Question

Wisitors have been asked to keep the woods clean and tidy.

Litter baskets have been placed under the trees.

People still throw their ribbish ever where.

I counted seven old cars and three old refrigerators.

Among the rubbish,I found a sign.
还有一句

What I saw made me very sad.

Answer 1

They(we/you/someone) have asked visitors to keep the woods clean and tidy.
They have place the litter baskets under the trees.
后面三句应该是主动改被动吧
Rubbish is thrown everywhere by those people.
Seven old cars and three old refrigerators were counted by me.
a sign was found among the rubbish.

Answer 2

They have asked the visitors to keep the woods clean and tidy.
They have placed the litter baskets under the trees.

their rubbish is still thrown everywhere by people.

Seven old cars and three old refrigerators were counted by me.

Among the rubbish, a sign was found by me.

Answer 3

They ask the visitors to keep the woods clean and tidy.

They place the litter baskets under the trees.

Rubbish are still thrown everywhere by people.

Seven old cars and three old refrigerators were counted by me.

Among the rubbish, a sign was found by me.