The correct answer is: A. each user can "see" only a small part of the entire database.
A large DBMS can be divided into multiple subschemas, each of which contains a subset of the data in the database. This allows users to only see the data that they need to, and prevents them from accessing data that they should not be able to see.
Option B is incorrect because not all users need to be able to access every subschema. For example, a user who only needs to view data about orders does not need to be able to view data about customers.
Option C is incorrect because not every subschema contains every field in the logical schema. For example, a subschema that contains data about orders may not contain data about customers.
Option D is incorrect because not all of the above statements are true.
Option E is incorrect because the correct answer is A.