To answer this question, we need to understand the concept of data hiding in the context of database management.
Option A) Conceptual level data hiding - This option is incorrect. Conceptual level data hiding refers to hiding the internal details and complexities of a database from the end-users. It is not directly related to hiding specific salary details from employees.
Option B) Physical level data hiding - This option is incorrect. Physical level data hiding refers to hiding the physical storage details and implementation specifics of a database from the end-users. It is also not directly related to hiding specific salary details.
Option C) External level data hiding - This option is correct. External level data hiding refers to hiding specific data elements or attributes from certain users or user groups. In this case, the manager's salary details are hidden from the employee, which is an example of external level data hiding.
Option D) All of these - This option is incorrect. While it is true that data hiding can occur at multiple levels (conceptual, physical, and external), the given scenario specifically relates to external level data hiding.
Option E) None of these - This option is incorrect. As explained above, the correct answer is Option C, which represents external level data hiding.
Therefore, the correct answer is C) External level data hiding.