> 
> Active: I want him to write the letter.
> 
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> Passive: I want the letter to be written/written by him(?).
> 
> 
> 

Can I use 'by him'? My grammar books didn't use it.

> 
> Passive - The poor girls are married at a young age.
> 
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> Active - The poor girls' parents marry them off at a young age.
> 
> 
> 

Is the active voice correct? And in the passive voice, shouldn't there be an 'off'? My book left it out.