Which concept stores data in blocks chained chronologically and immutable?

• A. Passwordless Authentication
• B. Blockchain
• C. Public Key Infrastructure
• D. Biometric Impersonation

Answer: (B)

Blocks of data are grouped together in a sequence where each block contains its own data plus a cryptographic link to the previous block, forming a chronological chain. This structure creates tamper-evidence: altering any earlier block would change its hash, which would break the link to the next block and alert the network. Because the ledger is distributed and requires consensus to add new blocks, rewriting history becomes computationally impractical. That combination—time-ordered blocks, cryptographic chaining, and distributed validation—produces true immutability. The other options don’t describe a system that stores information as linked blocks in a chronologically verifiable, tamper-resistant ledger.