When a relevant variable that is not named on either axis changes,

A) there will be a movement along the curve.
B) the curve will rotate clockwise.
C) the curve will be unaffected since only the variables on the axis affect the curve.
D) the curve will shift.

When a relevant variable not named on the axes changes, it affects the entire relationship represented by the curve, leading to a shift of the curve, rather than a movement along the curve or a rotation. This is because the change in the external variable alters the conditions under which the curve was originally drawn.