An enzyme speeds up a reaction by a. lowering the activation energy. b. raising the activation energy. c. releasing energy. d. absorbing energy.

Step 1: Define the Problem

Identify the key component of the question: Determine how an enzyme affects a chemical reaction.

Step 2: Break Down the Problem

The problem involves understanding the role of an enzyme in a chemical reaction, specifically regarding activation energy.

Step 3: Apply Relevant Concepts

Enzymes are biological catalysts that speed up chemical reactions. They do this by lowering the activation energy required for the reaction to occur.

Step 4: Analysis, Verify and Summarize

• Lowering Activation Energy: Enzymes provide an alternative reaction pathway with a lower activation energy.
• Raising Activation Energy: This would slow down the reaction, which is not the function of enzymes.
• Releasing Energy: This is not directly related to the function of enzymes in speeding up reactions.
• Absorbing Energy: This is also not related to the enzyme's role in catalysis.

Final Answer

a. lowering the activation energy.