Select the Letter Cluster that can replace the question mark (?) in the following series. ROB, URE, XUH, ?, DAN

BYL AYK AXK BXL

AXK

Explanation: ROB, URE, XUH, ?, DAN The logic followed here is : R → (+3) → U → (+3) → X → (+3) → A → (+3) → D O → (+3) → R → (+3) → U → (+3) → X → (+3) → A   B → (+3) → E → (+3) → H → (+3) → K → (+3) → N So, the letter-cluster that replaces the (?) to complete the series is "AXK"