1) Which describes the motion of a star across the sky over the
course of one sidereal day?
(a) Makes one complete circle around an axis through the
North Star.
(b) Makes slightly more than one complete circle around an
axis through the North Star.
(c) Makes an approximate circle around an axis through the
North Star, but does not return to the original point.
(d) Moves from west to east across the sky with occasional
loops in the opposite direction.
(a) is correct. (b) is what a star does in one solar day, not one
sidereal day. (c) is what a planet does in one sidereal day.
(d) is what a planet does over the course of many days.