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A logistics firm in Pune stores shipment records on a blockchain. An employee later discovers an error in block 50 and wants to change one entry. What happens to the hash linkage if the data in block 50 is altered?

Altering data in block 50 changes its hash, so the previous-hash value held in block 51 no longer matches. This break in linkage reveals the tampering, and an attacker would have to recompute all later blocks and win network consensus, which makes alteration impractical.

  1. AOnly block 50's hash stays valid and later blocks are unaffected
  2. BThe hash of block 50 changes, so the previous-hash reference stored in block 51 no longer matches, exposing the tamperingCorrect
  3. CThe hash of block 49 changes automatically
  4. DThe network deletes block 50 and re-issues the original

Explanation

Each block stores the hash of its predecessor. Changing block 50's data changes its hash, so block 51's stored reference mismatches and the chain breaks unless all later blocks are recomputed and accepted by consensus. Block 49 is unaffected since hashes depend on earlier content only.

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