In addition to water, what things are necessary for an aquifer to form?

a. acid and porous rocks
b. porous rocks and a cave
c. water table and an impermeable rock layer
d. porous rocks and an impermeable rock layer

The answer is; D

The porous rock is able to absorb water from precipitation. The water resides in the pores of the rock. The impermeable rock later, which does not allow water to pass through it, allows more water to hold in the porous rock and making the local water table to rise. The water in the porous rock, therefore, can be accessed through wells or a water spring can develop.

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products