1. Should they sell food on the sidewalk?
⇒should the food be sold on the sidewalk?
2. Nobody can answer the question correctly.
⇒the question could be answered correcly by nobody
3. Mr. Minh took the children to the zoo last week
⇒the children were taken to the zoo last week by mr.minh
4. They will open a new shopping mall in the neighborhood.
⇒a new shopping mall will be opened in the neighborhood
5. The government spent billions of dollars on cancer research last year.
⇒billions of dollars on cancer research were spent by the gorvermeny last year