Question

What is a 51% attack?

a) A condition in which more than half the computing power of a cryptocurrency network is controlled by a single malicious miner or group of miners

b) A second blockchain used by developers for testing new versions of client software without putting a real value at risk

c) An attack on a website where large numbers of request are made with the goal of shutting down the website

d) There is no such thing

Answer 1

Generally bitcoins and any other cryptocurrencies are based on blockchains which will be in the form of a distributed ledger.

They record the each and every transaction made on a cryptocurrency's network and are made available to all the users.

coming to 51% attach which refers to an attack on a blockchain for which such an attack is still hypothetical,by a group of miners or a single miner controlling more than half of the (50%) mining hashrate or computing power.

Therefore the answer is A)