Ethereum, DApps, and the Blockchain Ecosystem
Free EC-Council Certified Blockchain Professional practice — 6 questions on Ethereum, DApps, and the Blockchain Ecosystem, with explanations. No sign-up. Full 12-question mixed test →
A developer deploys a smart contract function that performs multiple sequential state-changing operations (e.g., updating three separate storage variables). During execution on the Ethereum Virtual Machine, the transaction runs out of gas after the second operation completes but before the third. Which statement BEST describes the outcome?
An out-of-gas exception is a hard EVM error: all state modifications within that transaction are rolled back atomically (as if the transaction never happened), but the gas already consumed executing the opcodes up to the failure point is still paid to the network and is not refunded.
A gaming platform needs to issue thousands of unique non-fungible in-game items alongside a fungible in-game currency, and wants the ability to transfer multiple token types of both kinds in a single batched transaction to minimize gas costs. Which Ethereum token standard BEST fits this requirement?
ERC-1155 is the multi-token standard that allows a single contract to manage both fungible and non-fungible token types, and supports batch transfers of multiple token IDs in one transaction, significantly reducing gas overhead versus deploying separate contracts.
Under Ethereum's EIP-1559 fee model, a user sets maxFeePerGas to 50 gwei and maxPriorityFeePerGas to 2 gwei for a transaction. The network's current base fee is 30 gwei. What fee does the validator actually earn per unit of gas, and what happens to the base fee portion?
EIP-1559 splits the transaction fee into a base fee (algorithmically set per block, always burned to reduce ETH supply) and a priority fee/tip (paid directly to the validator as an incentive for inclusion). Only the tip — capped at maxPriorityFeePerGas — goes to the validator.
Which statement correctly distinguishes an Externally Owned Account (EOA) from a Contract Account on Ethereum?
EOAs are the standard user accounts tied to a private/public key pair, hold no code, and can initiate transactions. Contract accounts are deployed with bytecode, have no private key, and execute their logic only when invoked by a transaction or an internal message call from another contract.
A supply-chain company wants a smart contract to automatically release payment only when a temperature-sensitive shipment's IoT sensor confirms the cargo stayed within a specified temperature range during transit. The smart contract cannot natively read data from the physical sensor. What blockchain component is REQUIRED to bridge this off-chain IoT data to the on-chain contract?
Smart contracts execute deterministically and cannot access external data sources directly. An oracle is the component designed to fetch, verify, and deliver off-chain data (such as IoT sensor readings) onto the blockchain so smart contracts can act on it — a core concept in the convergence of IoT and blockchain (BoT).
An organization wants to build a decentralized marketplace where AI model providers can prove their training datasets were not tampered with after collection, without exposing the raw underlying data itself. Which combination of blockchain properties makes this use case possible?
This is a canonical AI-blockchain convergence pattern: raw data is hashed off-chain, and only the resulting cryptographic hash (a fixed-size fingerprint) is committed on-chain with an immutable timestamp. Anyone can later re-hash the dataset and compare it to the on-chain record to verify integrity, without the blockchain ever storing or exposing the sensitive raw data.
Ready for the real thing?
The full course has two full-length practice tests, video lessons for every exam domain, hands-on labs and detailed answer explanations.
Start my full course on Udemy →