I have logged into oracle using SQLPLUS. When I type any kind of query, there is only 1 answer - '2'.
What is wrong with it?
That means your query is still incomplete and need more input from your side.
In your case, its probably because you didn't terminate the query with a semicolon.
When you get "2", type the semicolon ";" and enter.
Please also make sure, you terminate all your future queries with ";".
e.g.
select id from emp where id = 5;