When will BLP consider the information flow that occurs?

A.
When a subject alters on object.

B.
When a subject accesses an object.

C.
When a subject observer an object.

D.
All of the choices.

Explanation:
Bell-LaPadula is a state machine model capturing confidentiality aspects of access
control. Access permissions are defined through an Access Control matrix and through a

partial ordering of security levels. Security policies prevent information flowing
downwards from a high security level to a low security level. BLP only considers the
information flow that occurs when a subject observes or alters an object.