As shown by research, a stable marriage does not necessarily mean a(n) ______ marriage.

A．It means that one always knows what his muscles are doing.
B．It means that one performs simple actions without working.
C．It means that one’s muscles are used only to the extent necessary for each action they perform.
D．It means that one improves muscular action consciously.

A．Ask the stewardess for change.
B．Move to another part of the plane.
C．Sit where there is a breeze.
D．Extinguish his cigarette.