Help ... ... . . . .

D.

Explanation:

She's trying to find the affect different shapes have on the distance the plane flies, not the affect different types of paper have on distance. If she were to use different paper for each plane she'd be testing two variables instead of one.

hope this helps :)

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

-hails tea

explanation:

-t poses