Which of the following letter cluster will replace the question mark (?) to complete the given series? PTX, AEI, LPT, ?

XAE WZE XAD WAE

WAE

Explanation: PTX, AEI, LPT, ? The logic followed here is : P → (+11) → A → (+11) → L → (+11) → W T → (+11) → E → (+11) → P → (+11) → A X → (+11) → I → (+11) → T → (+11) → E  So, the letter-cluster that replaces the (?) to complete the series is "WAE"