CBCP Certified Blockchain Professional (CBCP) MCQ 4 — Questions and Answers
Question 1: In Solidity, what is the difference between 'storage' and 'memory' variable locations in smart contract execution?
- Storage is encrypted on-chain; memory is unencrypted during execution
- Storage persists permanently on-chain between calls; memory is temporary within a single call (Correct answer)
- Storage holds function parameters; memory holds state variables
- Storage is faster and cheaper; memory is slower and more expensive
Correct answer: Storage persists permanently on-chain between calls; memory is temporary within a single call
In Solidity, 'storage' variables are written to the blockchain and persist across transactions, while 'memory' variables exist only during a function call and are discarded afterward.
Question 2: What is the 'Oracle Problem' in smart contract design?
- Smart contracts cannot call Oracle database systems due to licensing restrictions
- Blockchains cannot natively access external real-world data without a trusted intermediary (Correct answer)
- Oracle nodes compete with miners for block rewards, creating congestion
- Smart contracts can only read Oracle data once per block due to consensus rules
Correct answer: Blockchains cannot natively access external real-world data without a trusted intermediary
The Oracle Problem describes the challenge that blockchains are deterministic closed systems unable to access real-world data natively, requiring external oracles that introduce trust assumptions.
Question 3: A DeFi protocol suffers a flash loan attack where an attacker borrows millions, manipulates an on-chain price oracle, and profits instantly. What is the root cause?
- Inadequate transaction fee incentives for validators
- Reliance on a single on-chain DEX spot price as an oracle without time-weighting (Correct answer)
- Smart contract code compiled with an outdated Solidity version
- Insufficient block gas limit preventing liquidation transactions
Correct answer: Reliance on a single on-chain DEX spot price as an oracle without time-weighting
Flash loan attacks typically exploit spot-price oracles drawn from a single DEX, which an attacker can manipulate within one transaction block; time-weighted average prices (TWAPs) mitigate this.
Question 4: Which property ensures that a blockchain transaction, once confirmed in sufficient blocks, cannot be reversed by any single party?
- Transparency
- Decentralization
- Finality (Correct answer)
- Pseudonymity
Correct answer: Finality
Finality (probabilistic or absolute depending on consensus mechanism) is the property ensuring a confirmed transaction cannot be rolled back, providing settlement certainty to participants.
Question 5: In enterprise blockchain governance, what is a 'permissioned' network's primary advantage over a public blockchain for regulated industries?
- Permissioned networks are always faster due to fewer nodes
- Permissioned networks allow known, vetted identities and regulatory compliance controls (Correct answer)
- Permissioned networks eliminate the need for consensus mechanisms entirely
- Permissioned networks have lower hardware requirements for node operation
Correct answer: Permissioned networks allow known, vetted identities and regulatory compliance controls
Permissioned blockchains restrict participation to vetted entities, enabling KYC/AML compliance, auditability by regulators, and governance controls required in finance, healthcare, and supply chain.
Question 6: What does the CAP theorem imply for distributed blockchain systems during a network partition?
- Blockchains must choose between consistency and availability when partitioned (Correct answer)
- Blockchains achieve all three CAP properties simultaneously through cryptography
- CAP theorem only applies to traditional databases, not blockchains
- Network partitions are impossible in PoW systems due to mining incentives
Correct answer: Blockchains must choose between consistency and availability when partitioned
CAP theorem states a distributed system can only guarantee two of Consistency, Availability, and Partition Tolerance; during a partition, most blockchains prioritize consistency (refusing to fork) or availability (allowing temporary forks).
Question 7: Which tokenization model represents fractional ownership of a real-world asset such as real estate on a blockchain?
- Utility Token
- Security Token (STO) (Correct answer)
- Stablecoin
- Non-Fungible Token (NFT)
Correct answer: Security Token (STO)
Security Tokens represent ownership stakes or financial rights in real-world assets and are subject to securities regulations, making them the appropriate model for tokenized real estate or equity.
CBCP Certified Blockchain Professional (CBCP) MCQ 4
In Solidity, what is the difference between 'storage' and 'memory' variable locations in smart contract execution?