Find the next number in the given series ?

3, 7, 6, 5, 9, 3, 12, 1, 15, . . .

In the following question, four number pairs are given. The number on left side of (–) is related to the number on the right side of (–) with some Logic/Rule/Relation. Three are similar on basis of same Logic/Rule/Relation. Select the odd one out from the given alternatives.

In the following question, select the odd word pair from the given alternatives.

In the following question, four groups of three numbers are given. In each group the second and third number are related to the first number by a Logic/Rule/Relation. Three are similar on basis of same Logic/Rule/Relation. Select the odd one out from the given alternatives.

In the following question, select the odd letter/letters from the given alternatives.

In the following question, four number pairs are given. The number on left side of (–) is related to the number of the right side of (–) with some Logic/Rule/Relation. Three are similar on basis of same Logic/Rule/Relation. Select the odd one out from the given alternatives.

In the following question, select the odd word pair from the given alternatives.

Rearrange the jumbled up letters to form a meaningful word and find the odd one out.

One of four words is a class of which the other three belong. Identify the class.