Ameans of expressing numbers as a multiple of two factors: a number between 1 and 10; and ten raised to a power, or exponent

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

d.embryo is the correct one