If the skater isn't holding on to anything, and there's no friction between the skates and the floor, then there's no way for any force to reach her and make her start moving.
-- No matter what the bus does, the skater stays right where she is.
-- But at the same time, the bus starts moving forward.
-- So if the bus-driver looks in his mirror, he see the skater moving down the aisle backwards, away from the driver, towards the back of the bus.
Answer:
As the bus backs up, the skater moves backwards
Explanation:
