The question: how can I rewrite these sentence in the present perfect passive ?
1- How long have we used computers ?
I couldnt rewrite the sentence ..!!
2- The researchers have discovered many new herbs since World War 1 .
My answer: Many new herbs have been discovered since Wold War 1.
3- Housemaid has cleaned the dressing trolleys with the antiseptic .
My answer: The dressing trolleys with the antiseptic have been cleaned.
4- The doctor has prescribed a medicine for the patient in bed 6.
My answer: A medicine for the patient in bed 6 has been prescribed .
5- The researchers have found sucrose in the stalk of many plants.
My answer: A sucrose in the stalk of many plants has been found .
6- Ms.Sara has published two books on study skills.
My answer: Two books on study skills have been published .
Finally , If you can explain to me how to rewrite .. or the rules that we have to follow .. to get the right structure of any sentence we rewrite?
Because I have a problem with this grammer topic when i change the structures... please help me