Why is she? Why he is not correct?
He, She, It ..All of them are correct
why is it not " she read them a book"?
Because this is not past tense, it is simple present tense :)
It should be "She reads them a book."
ok thank you
can we say
he reads them a book?
Same here. ''O'' is ''He'', ''She'', or ''It'', or the three of them?
It is situational. Depends on the context, it can be he or she. If its before stating a person, for example, "O erkek" it would mean "that" instead of he or she. Otherwise it is just he or she. Hope that helps!