下面哪个定义实现了函数map :: (a -> b) -> [a] -> [b]

A、map f ys = foldr (\x xs -> xs ++ [f x]) [] ys;

B、map f ys = foldr (\x xs -> f x ++ xs) [] ys;

C、 map f ys = foldl (\xs x -> f x : xs) [] ys;

D、map f ys = foldl (\xs x -> xs ++ [f x]) [] ys