1. Bitcoin mining is also known as proof-of-work (POW) because in order to create a valid block, the miner has to spent a significant amount of computational work to figure out a nonce, so that the hash of the nonce and the block to be proposed is adequately small. Which of the following is NOT a reason to include proof-of-work in the designs of permissionless blockchains?

A.

To randomly select nodes in proportion to their computing powers

B. To make mining so costly that miners have incentives to not create invalid blocks

C. To make it impossible for one miner to act like many different miners

D

To allow nodes to compete for the right to create blocks

2. What functions cannot

be currently performed by a smart contract without additional technological and economic designs?

A. Receive cryptocurrencies from other addresses and stop once a target is reached

B.

Receive cryptocurrencies from other addresses but undo all these transactions at the end of a specified time frame if a target is not met by then.

C.

Send cryptocurrencies to a specific address after 20 blocks

D.Send cryptocurrencies to a specific address if Washington Redskins wins the NFL.