Dave's ESL Cafe's Student Discussion Forums

[puzzle]

Dear teachers,
There is a proof reading exercise liike this:
"If the book you want is out ,you may ask it to be kept for you."
And the answer given is to add "for" after "ask".
But I think we usually say "ask sb. to do sth." ,so the passive voice should be "ask sth. to be done", why add"for" here. And we know "ask for"means require sth. Am I right?
Thank you!

[Lorikeet]

We also say, "ask for something."

John went to the library and asked for the book he wanted.
Peter asked his mother for some money for the movie.
Alice asked her brother for some help.