Final answer:
The true statement about enzymes is that they all lower the energy of activation. Enzymes catalyze reactions by reducing the minimum energy required for them to proceed and are not consumed by the reactions they help catalyze.
Step-by-step explanation:
The correct answer to the question 'Which of the following statements regarding enzymes is true?' is (d) All lower the energy of activation. Enzymes are biological catalysts that accelerate chemical reactions by lowering the activation energy, which is the minimum energy necessary for a reaction to occur. This does not mean that enzymes are consumed by the reaction—they are not changed or consumed at the end of the reaction and can be used repeatedly. The conditions under which enzymes operate, such as pH and temperature, can vary greatly depending on the enzyme in question. Some enzymes function optimally in acidic or basic conditions, and not necessarily at a neutral pH. Not all enzymes require a coenzyme, but many do not achieve optimal activity without certain cofactors or coenzymes. These can be metal ions (inorganic) or organic molecules, and they generally assist in the enzyme's activity by stabilizing its structure or participating in the catalytic process.