A. Cryptocurrency is a digital or virtual form of currency that uses cryptography for security. It is decentralized and usually based on blockchain technology.

C. Dollar is a type of fiat currency, not a cryptocurrency. Bitcoin, Ethereum, and Ripple are examples of cryptocurrencies.

C. Blockchain is a type of distributed ledger that records transactions across many computers in such a way that the registered transactions cannot be altered retroactively.

B. HODL is an investment strategy in the context of cryptocurrency. It means to hold onto the cryptocurrency and not sell it, even when the prices are falling.

C. ICO, or Initial Coin Offering, is a type of crowdfunding used by new cryptocurrency companies to raise capital. In ICO, some quantities of the newly issued cryptocurrencies are sold to investors in exchange for other established cryptocurrencies such as Bitcoin or Ethereum.

B. A cryptocurrency exchange is a platform that allows customers to trade cryptocurrencies for other assets, such as conventional fiat money or other digital currencies.