41.    They had exported the rice before May.  The rice    had been exported by them before May
42.    I had waited for her before I came here.  She    had been waited by me before I came here
43.    No one had met me before I left.  I   hadn't been met anybody before I left  
44.    He hadn’t eaten the cakes.  The cakes    hadn't eaten by him
45.    He might have caught the fish.  The fish  might have been caught by him  
46.    She could have washed the dress.  The dress   could be washed 
47.    She is not going to pick many flowers.  Many flowers  aren't going to be picked by her  
48.    Parents should give children a lot of love.  children    should be given a lot of love by Parents
49.    You must wash your hands.  Your hands  must be washed  
50.    He can speak four languages.  Four languages    can be spoken by him
51.    You must keep dogs outside shops.  Dogs    must be kept outside shops
52.    Children should treat old men with respect.  Old men    should be treated with respect by children 
53.    My classmates used to call me John.  I  used to be called John by my classmate
54.    He can’t repair my bike.  My bike can't be repaired by him