1. The problem asks which search method is best for finding a specific ID number in a stack. 2. A linear search checks each item one by one until it finds the target or reaches the end. 3. A binary search requires the data to be sorted and repeatedly divides the search interval in half. 4. Since a stack is typically unsorted, binary search cannot be used effectively. 5. Therefore, only linear search will work on an unsorted stack. 6. The correct answer is D: Only the linear search will work since the data has not been sorted.