Which of the following statements are TRUE?

A. If A's salary is 20% more than B, then B's salary is 20% less than A.

B. By selling 28 pens, a man gains the selling price of 4 pens. The gain is 15%.

C. The average of N consecutive natural numbers starting from 1 is \(\frac{(N+1)}{2}\).

Choose the correct answer from the options given below