Iwill give brainlist!
this is a bird's eye view of the location you see at the bottom of the image. it shows a topographic map of the area. compare
the two. one feature, a
is shown in the top topographic map as circles within circles.
a- canyon
b- mountain
c- plains
d- valley

im pretty sure a mountain

Explanation:

im like 95% sure but hey this is better than nothing

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

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