Final answer:
The tightest complexity of the code segment is O(n).
Step-by-step explanation:
The tightest complexity of the given code segment can be determined by analyzing the number of iterations the loop will undergo. The loop iterates from i = 0 until i < n, incrementing i by 1 in each iteration. Therefore, the loop will execute for a total of n times. In big O notation, this can be represented as O(n).