Final answer:
Gas fees are lower on PoS blockchains compared to proof-of-work blockchains. Answer b. proof-of-work is correct, as PoW requires significant computational effort, leading to higher transaction fees. PoS operates on staking, making it more energy-efficient and cost-effective.
Step-by-step explanation:
Transaction fees, often referred to as gas fees, are generally lower for transactions on Proof of Stake (PoS) blockchains compared to those on proof-of-work blockchains. The correct answer to the question is b. proof-of-work. Proof-of-work blockchains like Bitcoin and Ethereum (as of the knowledge cutoff in 2023) require significant computational effort to validate transactions and add them to the blockchain, which in turn can lead to higher transaction fees.
Conversely, PoS blockchains are designed to be more energy-efficient and typically result in lower fees due to a different transaction validation mechanism, where validators are chosen based on the number of coins they hold and are willing to 'stake' as collateral, rather than the computational work performed.