Can someone me i don't understans

The question is asking which formula will give the results
1, 9, 36, 100, 225, ...
for k values of
1, 2, 3, 4, 5, ...

You can try them out to see.
A) for k=2, gives 2*3/2 = 3 . . . not 9
B) for k=1, gives 2^3/3 = 8/3 . . . not 1
C) for k=2, gives (2^2*3^2)/4 = 9 . . . . looks promising
D) for k=1, gives 1*2^3/5 = 8/5 . . . not 1

Selection C is the only viable choice. (And the correct one.)

D.