Q: The three concepts used to explain the foundation of blockchain are __________________.  

Distributed Network, Cryptography, Public Ledger.

These three concepts form the foundation of blockchain technology. The distributed network allows for multiple nodes to participate in the network and validate transactions, creating a decentralized system. Cryptography provides secure communication and data privacy, ensuring that transactions on the blockchain are secure and tamper-proof. The public ledger records all transactions on the blockchain in a transparent and immutable way, allowing for anyone to verify and track the history of transactions. Together, these concepts enable trust and transparency in a decentralized system, making blockchain a revolutionary technology for many industries.