"They write us a book."

Translation: Ils nous écrivent un livre.

[allhaze]

Why is 'ils on ecrivent un livre' unacceptable?

[Sitesurf]

"on" is not an exact substitute for "nous", especially because it only exists as a subject.

[Hector290697]

It works just like "Ellos nos escriven un libro" in Spanish.

[NoirinNica]

As in the similar sentence in the singular that appeared earlier in the exercise the structure of the English sentence is poor. To a native speaker 'They write us a book' is not a well written sentence. For example, ' He writes them a letter' means 'he writes a letter to them'. What this exercise meant was 'They write a book for us' not ' to us'. In the construction 'writes us' a 'to' is implied but a 'for us' must be written explicitly.

[keventurnbull]

Couldn't this also be "Vous nous ecrivez un livre."?

[Sitesurf]

No, "vous" is you (polite or plural), not ils/elles = they

[lai_mesunda]

Can "Eux" replace "Ils" for this sentence?

[Sitesurf]

Yes, if you mean to emphasize the fact that "they" are doing something different from what others are doing.

[NaftaliFri1]

Well, just marked me wrong... Reported.