The right answer is to measure the amount of released carbon dioxide.
The carbon dioxide exhaled by the lungs can reflect the energy consumed by the body since it comes from the degradation of glucose which is the main energy substrate. And this is a better indicator of energy consumption than measuring heart rate because it can be inflected by several factors.
A is false because glucose is not found in the urine, except in the case of diabetes mellitus.
C is false because the consumption of calories does not mean that we will directly use it.
D is wrong because perspiration is independent of energy consumption, this is a way to cool the body after exercise.
Arthropoda and molluscs have open circulatory systems - meaning haemolymph (Their equivalent to blood) directly bathes the tissue, and isn't enclosed in blood vessels, as seen in a closed blood system, as in humans for example.
Enzymes can be denatured by irregular PH. Meaning that they can change shape. Enzymes rely on their shape in order to function so if their shapes change because of the PH then the active sites don't fit anymore and they enzymes wont work.