Verbal Reasoning - Mental Ability Questions

The correct order is :   

Newly married Couple     Family    Caste    Clan    Species

                      3                        2                1             4             5

The cat's foot is called a paw. The horse's foot is called a hoof.

The first digit is formed by adding the numbers which are the results of powers of 2 increased by one and second letter is the corresponding alphabet to that number...last number is the next number to the first one...therefore

15=7+8 (i.e. 2^3)

O is corresponding alphabet to 15

and 16 comes after 15 

Here the given number analogy follows two patterns that,

6 

18 --> 6 x 3

4

12 --> 4 x 3

OR

6

18 ----> 6x6/2 = 18

4

8 ----> 4x4/2 = 8

As 12 is not available in the options, 8 is correct answer.