What is the purpose of the delete operator in

Three of the following four letter-clusters are alike in a certain way and one is different. Choose the odd one.

Four of the following five are somehow similar and therefore create a group. Which is not related to this group?

U, F, Z, O, S

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

Pick the odd one out:

Four numbers are given, three of which are alike in certain manner and one is different. Choose the different number.

Three of the following four are alike and hence formed a group. Which is the one which does not belong the group?

Four of the following five pair of letter cluster are alike in a certain manner and one is different. Select the one which is different.

Three of the following four numbers are alike in a certain way and one is different. Pick the number that is different from the rest.

Three of the four words are alike in a certain way and one is different. Pick the odd one out.