BKK, EII, HGG, (?), NCC

Answer: KEE

Key pattern: the first letters advance by +3, while the middle and last letters are identical and decrease by 2.

• Step 1: First letters — B, E, H, ?, N correspond to positions 2, 5, 8, ?, 14. These increase by 3 each time, so the missing first letter is position 11, which is K.

• Step 2: Middle and last letters — K, I, G, ?, C correspond to positions 11, 9, 7, ?, 3. These decrease by 2 and are identical in each entry, so the missing middle and last letters are position 5, which is E (giving EE).

• Step 3: Combine results — first letter K and middle+last EE produce KEE, which fits the sequence BKK, EII, HGG, KEE, NCC.