We'll try and eliminate the wrong options
when K = 4 ==> $\dfrac{(4 + 2)^2}{(4 - 3)}$ = 36 (integer)
when K = 8 ==> $\dfrac{(8 + 2)^2}{(8 - 3)}$ = $\dfrac{(100)}{(5)}$ = 20 (integer)
when K = 10 ==> $\dfrac{(10 + 2)^2}{(10 - 3)}$ = $\dfrac{(144)}{(7)}$ = 20.57 (not an integer)
when K = 16 ==> $\dfrac{(16 + 2)^2}{(16 - 3)}$ = $\dfrac{(324)}{(13)}$ = 24.92 (not an integer)
when K = 18 ==> $\dfrac{(18 + 2)^2}{(18 - 3)}$ = $\dfrac{(400)}{(15)}$ = 26.66 (not an integer)
when K = 26 ==> $\dfrac{(26 + 2)^2}{(26 - 3)}$ = $\dfrac{(784)}{(23)}$ = 34.08 (not an integer)
when K = 28 ==> $\dfrac{(28 + 2)^2}{(28 - 3)}$ = $\dfrac{(900)}{(25)}$ = 36 (integer)
By Verifying all the options we found out the correct option as C) 4, 8, 28