What is a Blockchain?

What does each block store that makes the blocks a chain?

• The names of everyone who will receive coins in the next block
• The hash of the block before it
• A copy of every earlier block

Every node has a copy of the chain, and all copies agree. Does that prove each entry is correct?

• Yes, because many copies can't all be wrong
• No; it proves the entries weren't changed, not that they were right when written
• Yes, as long as the chain is more than a day old