Select the term that will come next in the following series. GN, MT, SZ, ____

YF ZG XE WD

YF

Explanation: GN, MT, SZ, ____ The logic followed here is : G → (+6) → M → (+6) → S → (+6) → Y  N → (+6) → T → (+6) → Z → (+6) → F So, the letter-cluster that replaces the (?) to complete the series is "YF"