Which term best completes the sentence: A(n) _____ is a substance that speeds up a chemical reaction without being consumed in the process.

• A. catalyst
• B. product
• C. inhibitor
• D. reactant

Answer: (A)

Verified step by step guidance

1. Understand the definition of each term: A 'product' is a substance formed as a result of a chemical reaction; a 'reactant' is a substance that participates in and is consumed during a chemical reaction; an 'inhibitor' is a substance that decreases the rate of a chemical reaction.
2. Recall that a 'catalyst' is a substance that increases the rate of a chemical reaction without being consumed or permanently altered in the process.
3. Analyze the sentence: 'A(n) _____ is a substance that speeds up a chemical reaction without being consumed in the process.' The key phrase here is 'speeds up' and 'without being consumed.'
4. Match the definition of 'catalyst' to the sentence because it fits both criteria: it speeds up the reaction and remains unchanged after the reaction.
5. Conclude that the correct term to complete the sentence is 'catalyst.'