下列程序是二分法的程序，横线处应该填上（）。 def binary_search(arr, target): left = 0 right = len(arr) - 1 while left <= right: mid = (left + right) // 2 _________________________ return -1

A： if arr[mid] == target: return mid elif arr[mid] > target: right = mid - 1

B： if arr[mid] == target: return mid elif arr[mid] > target: right = mid else: left = mid

C： if arr[mid] == target: return mid elif arr[mid] > target: right = mid - 1 else: left = mid + 1