Very simply. 
( ( Very simply ) . )
(ROOT (NP (CD Very) (RB simply) (. .)))
Only a little explanation was needed.
( ( Only ( a ( little explanation ) ) ) ( ( was needed ) . ) )
(ROOT (S (NP (RB Only) (DT a) (JJ little) (NN explanation)) (VP (VBD was) (VP (VBN needed))) (. .)))