Change the sentences from Active Voice to Passive Voice

1)the sweets had been eaten ,when i came home
2)This book was written in 19th century 
3)A number  of important experiments has bing мейд in this laboratory
4)A new president is elected by people every four years in the USA
5)He will be operated by  the doctor in a week 
6)Streets are bing cleaned by the workers from rubbish 
7)Very delicious food was bing мейд by my mother ,when i came home 
8)This program can be used in my internet project 
9) Two foreign languages are studied by our pupils