Answer: (c)

Explanation:
Statement evaluation in light of blockchain technology:

Statement 1 is correct. In a blockchain, records can be made visible to relevant stakeholders depending on the type (public, private, or permissioned chains). Once recorded, data cannot be altered easily, ensuring transparency with integrity.

Statement 2 is correct. Blockchain operates on a distributed ledger system, where copies of the entire database are stored across multiple nodes in the network. These nodes synchronize frequently (often within seconds to minutes depending on the system), ensuring consistency.

Statement 3 is incorrect. A consortium blockchain is not a "blend of public and private blockchains." Instead, it is a permissioned blockchain governed by a group of organizations, not open to the public. This statement describes a Hybrid Blockchain, which seamlessly blends essential components of both open public networks and highly locked private setups to create customizable, selective public visibility walls.

Statement 4 is correct. Blockchain uses cryptographic hashing and consensus mechanisms, making it practically immutable-data cannot be changed or deleted once validated and added to the chain without altering subsequent blocks and consensus across the network.

Therefore, the correct statements are 1, 2, and 4, making the answer (c).