A dung beetle that has shaped a ball of dung must push it away from the crowded pile along a straight path, or rivals will steal it, and the beetles manage this even on moonless nights. Biologists agree that the beetles steer by the night sky. Some propose that they use the broad, faint band of light of the Milky Way as a whole, while others propose that they use the positions of individual bright stars, which would make the beetles' task much like that of a human navigator picking out stars.
hard
Which finding, if true, would most directly support the proposal that the beetles steer by the band of the Milky Way?
A Beetles rolled their balls in straight lines under an artificial sky that showed only the band of the Milky Way, but rolled in random directions under an artificial sky that showed only a handful of its brightest stars. B Beetles rolled their balls in straight lines under a sky showing the full pattern of the stars, although they did so less accurately on nights when clouds hid some parts of the sky from them. C Beetles lost the ability to roll their balls in straight lines when the brightest stars in the sky were hidden, but kept it when only dim stars that are faint and spread out were hidden. D Beetles rolled their balls in straight lines under the light of a full moon, and rolled them in randomly chosen directions when clouds had hidden the moon from the beetles' view.
Math 
