What is Blockchain?

• A. An encrypted, distributed database shared across multiple computers or nodes that are part of a community or system.
• B. A centralized ledger stored on a single server.
• C. A type of database used only for cryptocurrencies.
• D. A process for encrypting emails.

Answer: (A)

Blockchain is a decentralized, tamper‑evident ledger that’s distributed across many computers in a network. It stores data in blocks that are linked together cryptographically, with each block containing a set of transactions and a reference to the previous block. Because many participants hold copies and the network uses a consensus mechanism to agree on the state, no single party can change records without others noticing. This makes the system secure, transparent, and verifiable. It isn’t a centralized ledger on one server, isn’t limited to cryptocurrencies, and isn’t a method for encrypting emails.