21. Recall, a hash function, h, is a function that maps input of any size to output in some finite set. For example, in class we saw a hash function that takes as input any String and outputs a number between 0 and 25, according to the lexicographical ordering of the first letter of the String. What is a collision in the context of hashing? (A) When several keys are the same and entries get over-written. (B) When more than one key is hashed to the same output value. (C) When two different hash tables have the same name. (D) When a key is hashed to a value that is too large to fit in the array. (E) When a key is hashed and the output is the same as the input.