Three of the following letter-clusters are alike in some manner and hence form a group. Which letter-cluster does not belong to that group?

Based on the English alphabetical order, three of the following four letter groups are alike in a certain way and form a group. Which letter group does not belong to that group?
(Note: The odd letter group is not based on the number or position of vowels/consonants.)

Based on the English alphabetical order, three of the following four letter-clusters are alike in a certain way and thus form a group. Which letter-cluster DOES NOT belong to that group?
(Note: The odd one out is not based on the number of consonants/vowels or their position in the letter-cluster.)

Based on the alphabetical order, three of the following four are alike in a certain way and thus form a group. Which is the one that does not belong to that group?
(Note: The odd one out is not based on the number of consonants/vowels or their position in the letter cluster)

Based on the English alphabetical order, three of the following four letter-cluster pairs are alike in a certain way and thus form a group. Which letter-cluster pair DOES NOT belong to that group?
(Note: The odd one out is not based on the number of consonants/vowels or their position in the letter-cluster.)

Based on the English alphabetical order, three of the following four letter cluster pairs are alike in a certain way and thus form a group. Which is the one that does not belong to that group?

Based on the English alphabetical order, three of the following four letter-cluster pairs are alike in a certain way and thus form a group. Which letter-cluster pair DOES NOT belong to that group?
(Note: The odd one out is not based on the number of consonants/vowels or their position in the letter-cluster.)

Based on the English alphabetical order, three of the following four letter-clusters are
alike in a certain way and thus form a group. Which letter-cluster DOES NOT belong to that group?
(Note: The odd one out is not based on the number of consonants/vowels or their position in the letter-cluster.)

Four pairs of letter-clusters have been given out of which three are alike in some manner and one is different. Select the one that is different.

Three of the following four letter-clusters are alike in a certain way and thus form a group. Which letter-cluster does not belong to that group?

Three of the four groups of number-letters are alike. Which does not belong to the group?