Sorry I pressed Enter and it was posted. Can't edit it.
Assuming each student has only 1 book, should I say :
"I need to collect the students' book" OR
"I need to collect the students' bookS" ?
In general, if I have : <NOUN_1 IN PLURAL>'S NOUN_2
When should NOUN_2 be in plural form and when should it be in singular form ?
Thank you very much for your help.