_______ is a device used by navigators to find the directions.
A movable pulley is used as :
(a) a force multiplier
(b) a speed multiplier
(c) a device to change the direction of effort
(d) an energy multiplier
____________is a device used by navigators to find the direction.
________ is a device used by pilots and navigators to find the direction.
____________is a device which was used by pilots and navigators to find the direction.