The users responsible for query processing in database system are . . . . . . . .

This question asks about who is responsible for running queries in a database system. Let's break down the options:
Option A: Native users - This term isn't commonly used in database contexts.
Option B: Application programmers - These are developers who create software that interacts with databases. They often write code that includes queries to retrieve or modify data.
Option C: Sophisticated users - This is too broad. While some sophisticated users might write queries, this doesn't make them the primary group responsible.
Option D: Specialized users - Similar to Option C, this term is too general and doesn't specifically refer to database queries.
The most likely answer is Option B: Application programmers. They are the ones who directly work with database queries as part of their software development.