What is defined as a linear search?

A linear search is defined as a method that checks each element in a list or array sequentially until the target element is found or until all elements have been checked. This search algorithm does not make any assumptions about the order of the elements in the list, meaning it can work effectively on both sorted and unsorted data. The process involves starting from the first element and moving through each subsequent element until either the desired value is encountered or the end of the list is reached, making it simple and straightforward to implement.

In contrast, the other options describe different search techniques or conditions. For instance, finding the middle element of a sorted array pertains to binary search, which operates on the principle of divide and conquer rather than checking each element sequentially. Similarly, utilizing a binary tree for searching refers to a different structure and searching method entirely. Lastly, requiring the list to be sorted is a characteristic of algorithms like binary search, which operates only on sorted data, not linear search. Thus, the first definition accurately captures the essence of a linear search.