Observe the following table and figures related to a physical model of a river. What can be concluded about the velocity of the river with and without energy dissipation structures?
The velocity of the river is lower when there are free fall concrete spillways compared to stepped spillways in gabion.
The velocity of the river is higher when there are no energy dissipation structures.
The velocity of the river with stepped spillways in gabion is lower than without energy dissipation structures in most points.
The velocity of the river with stepped spillways in gabion is higher than without energy dissipation structures in most points.

a) 1 and 2 are correct.
b) 2 and 3 are correct.
c) 1 and 4 are correct.
d) 3 and 4 are correct.