Translation:Kitabu cha mwanafunzi
It depends on the noun class of the word before it.
cha mwanafunzi. = The student's book.
vya mwanafunzi. = The student's book
la mwanafunzi. = The student's name.
ya wanafunzi. = The students' name
There's a table of all the forms of this word here: https://en.wiktionary.org/wiki/a#Swahili You'll have to press "show" on the purple-grey bar saying "inflection" to open it.