To answer this question, let's go through each option to understand why it is correct or incorrect:
Option A) multiple DBDs for each database - This option is incorrect. In a database management system, there is typically one DBD (Database Description) for each database. The DBD contains information about the structure and organization of the database.
Option B) none of these - This option is incorrect.
Option C) cannot be used by DL/I - This option is incorrect. DBD (Database Description) is used in conjunction with DL/I (Data Language/I) to access and manipulate data stored in hierarchical databases.
Option D) created by a process called DBDGEN - This option is correct. DBD (Database Description) is created using a process called DBDGEN. DBDGEN is a utility that generates the DBD based on the database schema and specifications.
Therefore, the correct answer is option D) created by a process called DBDGEN.