Which letter will replace the question mark (?) in the following series? AB, BD, CF, DH, ?

EJ FK EK FJ

EJ

According to the above alphabet position: AB ⇒ (1) × 2 = (2) BD ⇒ (2) × 2 = (4) CF ⇒ (3) × 2 = (6) DH ⇒ (4) × 2 = (8) ? ⇒   (5) × 2 = (10) = EJ (add 1 in 1st alphabet position and do twice of 1st in 2nd alphabet position)