how to calculate Bubble sort Time Complexity

Question

I was trying to understand the Data Structure and different algorithm, then i got confused to measure the Bubble sort time complexity.

for (c = 0; c < ( n         


        

Answer 1

O(n^2) = n(n-1)/2 is the right one.

As in the above example of 5 elements.

5(5-1)/2 == 10.

5(5+1)/2 != 10.