Final answer:
Once a ball is fully submerged in water without touching the beaker's bottom, the spring scale reading decreases due to the upward buoyant force from water displacement.
Step-by-step explanation:
When a ball is fully submerged in water but does not touch the bottom of the beaker, the reading on the spring scale attached to the ball will show a decrease. This is due to the buoyant force that acts on the ball when it is in the fluid, which reduces the overall weight the spring scale measures. The buoyant force is equal to the weight of the water displaced by the ball, according to Archimedes' principle. If this upward buoyant force is equal to the weight of the ball, the ball remains suspended, and the scale reflects only the small additional force required to keep the ball submerged without touching the bottom.
Thus, the correct answer to the posed question is: b) The reading will decrease.