Which of the following best describes the cycle of matter between humans and the environment? Humans exhale carbon dioxide, which plants use in cellular respiration.
Humans inhale oxygen from plants, which is used in cellular respiration to produce water.
Humans inhale oxygen from plants, which is used in photosynthesis to produce carbon dioxide.
Humans exhale carbon dioxide, which plants use in photosynthesis to produce more carbon dioxide.

i think that d. wind is the answer.   i missed the question when i answered a. currents.

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

i think the answer would be a. after sentence 14! i hope i at least a little