Hi nipunranjan,
The GMAT consists of 4 Reading Comp questions with approximately 14 questions spread across the 4 passages. The subject matter will vary, but you're almost always going to see 1 "business" passage and 1 "science" passage. As you do better and better in the Verbal section, you're likely to see additional science passages. Since RC is such a big chunk of the Verbal section, it's important to learn the proper techniques for reading and taking notes as well as the various RC question types and the proper approaches for each of them.
GMAT assassins aren't born, they're made,
Rich