"Dia" is for either "he" or " she". https://www.duolingo.com/dictionary/Indonesian/dia/1d081cc665403ad7dc506f9996b64d6d
But ..... dia menulis buku? Is it correct as well? And I see all the lessons there are not used sebuah and double word for plural as well. I understand then plural is used there is no misunderstanding, but in some cases you cant understand from the sentence is it plural or not.
No. Just no.
- "He is (currently) writing a book"
- "He (just/previously) wrote a book" or at best: "He is (now) writing a book".
There is NO "he writes a book"! (With rare exceptions like weird literary uses like "In protest, he writes a book to rebel against them" or something. It's VERY uncommon.
In kindergarten and first grade, children write books very often. They are very short books, about eight to twelve pages long. “He writes a book.” can happen then also. You are thinking that writing a book is a long ongoing thing, but not always, sometimes it is a repetitive thing.
No, they actually make book covers for them. These are books with very simple language for very young readers. A short story can have quite difficult and long sentences that they wouldn’t even be ready to read yet. A writing exercise could be on multiple pages, but it would not have a book cover and does not necessarily have a story plot.