I need help with this pleasee

A   The oldest rock layer will occur at the bottom of the sequence

Explanation:

A) At the bottom of the rock sequence

Explanation:

If undisturbed, rock layers will build up over time, leaving the oldest ones on the bottom as new layers are on the top.

after receiving a stimus, the sensory receptors send(s) signals to the appropriate area of the body.  

the must be sensory neurons.  

hope its .

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