How Do Two Unequal-Mass Stars in a Binary Star System

Multiple Choice

How do two unequal-mass stars in a binary star system move around each other, in general?

A) The stars move in a single circular orbit around the same center and always on opposite sides from each other.
B) The stars move in straight lines, back and forth past each other.
C) The low-mass star moves in a circular orbit around the high-mass star, which remains stationary.
D) The stars move in elliptical orbits about a common center of mass.