why is this the right answer?

Consider the function fun :: Num a => [a] -> [a] fun (x:y:xs) = (x + y): (fun (y:xs)) fun _ = 0 Which is the best description of the return value (RETURNS) of fun l? Select one alternative: The pairs of consecutive elements of I A list of numbers that is shorter than I A list of consecutive elements of I Lists of consecutive elements of The sums of consecutive elements of