Answer: b. a lower price for wooden bats.
Step-by-step explanation:
If aluminum bats were permitted for use in baseball then a lot of teams would begin to use them instead. This would reduce the demand for wooden bats and lead to their prices falling.
The reason the price will fall is that the demand curve for the wooden bats will shift to the left to show that the demand has fallen. The curve would then intersect with the supply curve at a lower equilibrium price.
Essentially what happens is that, with people demanding less wooden bats, their prices would have to fall to entice people to buy them.