9. Vaccines have contributed to human population growth by lowering the death rate.
c. increasing the birthrate.
b. increasing the death rate.
d. lowering the birthrate.
a.
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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

sound moves fastest in solids because the molecules are tightly packed and it allows sound to vibrate