method in an object-oriented system is
the code that defines the actions that the object performs in response
to a message.
Answer "The means of communication among objects" is incorrect because it defines a message.
Answer "A guide to the programming of objects" is a distracter.
Answer "The situation where a class inherits the behavioral characteristics of more that one parent class" refers to multiple inheritance.

Explanation/Reference:
Explanation:
A gateway works at OSI Application layer, where it connects different types of networks; performs protocol and format translations.
Incorrect Answers:
A: A bridge works at the data link layer, not the application layer.
B: A repeater works at the physical layer, not the application layer.
C: A router works at the transport layer, not the application layer.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, New York, 2013, p. 623

In Discretionary Access Control (DAC) environments, the user who creates a file is also considered the owner and has full control over the file including the ability to set permissions for that file.
The following answers are incorrect:
Manager is incorrect because in Discretionary Access Control (DAC) environments it is the owner/user that is authorized to grant information access to other people group leader. Is incorrect because in Discretionary Access Control (DAC) environments it is the owner/user that is authorized to grant information access to other people security manager. Is incorrect because in Discretionary Access Control (DAC) environments it is the owner/user that is authorized to grant information access to other people.
IMPORTANT NOTE:
The term Data Owner is also used within Classifications as well. Under the subject of classification the Data Owner is a person from management who has been entrusted with a data set that belongs to the company. For example it could be the Chief Financial Officer
(CFO) who is entrusted with all of the financial data for a company. As such the CFO would determine the classification of the financial data and who can access as well. The Data
Owner would then tell the Data Custodian (a technical person) what the classification and need to know is on the specific set of data.
The term Data Owner under DAC simply means whoever created the file and as the creator of the file the owner has full access and can grant access to other subjects based on their identity.

In computer science, hierarchical protection domains, often called protection rings, are a mechanism to protect data and functionality from faults (fault tolerance) and malicious behavior (computer security). This approach is diametrically opposite to that of capability-based security.
Computer operating systems provide different levels of access to resources. A protection ring is one of two or more hierarchical levels or layers of privilege within the architecture of a computer system. This is generally hardware-enforced by some CPU architectures that provide different CPU modes at the hardware or microcode level. Rings are arranged in a hierarchy from most privileged (most trusted, usually numbered zero) to least privileged
(least trusted, usually with the highest ring number). On most operating systems, Ring 0 is the level with the most privileges and interacts most directly with the physical hardware such as the CPU and memory.
Special gates between rings are provided to allow an outer ring to access an inner ring's resources in a predefined manner, as opposed to allowing arbitrary usage. Correctly gating access between rings can improve security by preventing programs from one ring or privilege level from misusing resources intended for programs in another. For example, spyware running as a user program in Ring 3 should be prevented from turning on a web camera without informing the user, since hardware access should be a Ring 1 function reserved for device drivers. Programs such as web browsers running in higher numbered rings must request access to the network, a resource restricted to a lower numbered ring.
Ring Architecture
All of the other answers are incorrect because they are detractors.
References:
OIG CBK Security Architecture and Models (page 311)
and
https://en.wikipedia.org/wiki/Ring_%28computer_security%29