Please choose correct options. Thanks. a) The blocks in bitcoin's blockchain are put together with what kind of data structure? A hash chain of blocks O A doubly linked list of blocks A hash table of blocks O A binary tree of blocks b) Bitcoins' blockchain is using the SHA-256 hash function. What method does it use to convert an arbitrary-length input to a fixed length before applying the hashing. It applies a discrete fourier transform on the input. It iteratively compresses the input. It truncates the input to reach the desired length. It removes the least significant bits of the input. It's padding the input with zeros to reach the desired length