reading or studying

You want "studying" for material on which the student is to be tested. "Reading" has two problems. First, in Britain, one reads for or reads a subject to get a degree in that subject. The second is illustrated by #3. You mean to say that Javad is reading about the Arabic language, but the sentence says that Javad is reading something, anything that happens to be written in Arabic.

Thank you. But in addition to your explanation. Let me know exactly which one is more common to say ....
exactly 1 or 2

and

exactly 3 or 4?

What isn't clear about "You want 'studying'"?

Ok, thank you. Then just 2 & 4 are correct.

2. Javad is studying his lessons. 4. Javad is studying Arabic. He has an exam tomorrow. right?

Right.

sunny1232. Javad is studying his lessons.

This is weird and its meaning is unclear.

A lesson is a portion of learning assigned to a student.

Q: What is Javad doing now?
A: He's studying his lessons.

Instead of contemplating his girlfriend's picture or listening to downloaded music, he's studying the subjects his teachers have assigned. I might prefer "He's doing his homework" or just "He's studying," but I find the locution neither weird nor u

Please also let me know .... Which one do you prefer between these two?
A: Where is your son Javad?

1. He is upstair, He's studying his books.
or
2. He is upstair, He's reading his books.
?

Upstairs.

In response to a question about where your son is, all you need do is give a location. Upstairs. You're done.

"Studying" can have a connotation of closely observing, so "studying his books" gives the uncomfortable feeling that he may be looking at the books but not reading them.

My preference:

Q. Where is your son?
A. Upstairs, studying

deadratWhat fault do you find with it?

Lessons are something that people do so, how or why would they be studied? Does this mean analysing how a lesson was conducted, perhaps for the purpose of finding out how well a teacher taught? It's not clear.