If B says that “his mother is the only daughter of A’s mother” how is A related to B?

Which one is odd from the others?

What is the minimum number of cars that could move in the following format? Two cars in front of a car, two cars behind a car and a car between two cars:

How many 9’s are there preceded by 3 in the given sequence? 

896739378394563969

In a certain code SISTER is 535301, UNCLE as 84670, and BOY as 129, how is SON coded?

If in a certain code EXIST is coded as ESIXT, how is PLUTO coded in the same language?