Which of the following letter-clusters should replace # and % so that the pattern and relationship followed between the letter-cluster pair on the left side of :: is the same as that on the right side of :: ?
# : ACG :: CEI : %​

Given: # : ACG :: CEI : %

Logic: 1st and 3rd three letters are increasing + 4 place.

Now, we check each options.

Option (a): # = WYC , % = GIK (Not Follow)

W + 4 = A, Y + 4 = C, C + 4 = G

C + 4 = G, E + 4 = I, I + 4 $$\neq$$​ K

Option (b): # = WYC , % = KIM (Not Follow)​

W + 4 = A, Y + 4 = C, C + 4 = G

C + 4 $$\neq$$​ K, E + 4 = I, I + 4 = M

Option (c): # = XYC , % = GIM (Not Follow)​

X + 4 $$\neq$$​ A, Y + 4 = C, C + 4 = G

C + 4 = G, E + 4 = I, I + 4 = M

Option (d): # = WYC , % = GIM (Follow)​

W + 4 = A, Y + 4 = C, C + 4 = G

C + 4 = G, E + 4 = I, I + 4 = M

Thus, correct option is (d).