Select the option that is related to the fifth term in the same way as the second term is related to the first term and fourth term related to third term.

786 : 7 :: 645 : 5 :: 282 : ?

4

Pattern followed is :

Sum of the digit of first number is divided by 3 to get the 2nd number.

786 : 7        

7 + 8 + 6 = 21

21 ÷ 3 = 7

& 645 : 5

6 + 4 + 5 = 15

15 ÷ 3 = 5

Similarly ,

282 : ?

2 +  8 + 2 = 12

12  ÷ 3 = 4

4 , is correct answer .