Question

enzymes function by:
stopping chemical reactions
lowering the activation energy needed for reactions
increasing the bodys temperature
acting as a source of energy

Explanation:

Enzymes are biological catalysts. Catalysts work by lowering the activation energy (the minimum energy required for a chemical reaction to occur). They do not stop reactions (they speed them up), do not act as an energy source (that's what molecules like ATP are for), and do not increase body temperature (that's regulated by other physiological mechanisms).

Answer:

Lowering the activation energy needed for reactions