Which systems work together so oxygen can be distributed to the cells of the body?
How do these two systems work together to accomplish this tasks?

The sample response:

The respiratory and the circulatory systems work together to bring oxygen to the cells in the body. The respiratory system takes oxygen from the air to the lungs, where the oxygen is transferred to the blood. The circulatory system transports the blood, which delivers oxygen to the cells in the body.

Explanation:

i think the answer would d

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