D, you're adding numbers and it will just print the result in integers not in string format.
You have 4 basic types of data in Python:
Integer -> non-decimal number i.e. 1,2,3,4,5...
Float -> decimal number
i.e. 0,128
Boolean -> true or false
(that is clear enough I think?)
String -> text as in a textbook i.e. You won the lottery.