What happens in a Call/Return pattern?

• A. a calling operation in the calling object sends a message to an operation (a.k.a. method) in the called object.
• B. a calling operation in the calling object invokes an operation (a.k.a. method) in the called object.
• C. the calling object waits for a response from the called object.
• D. the calling object does not wait for a response from the called object.