( ( These elements ) ( ( are ( separated ( by ( an ( air gap ) ) ) ) ) . ) )
(ROOT (S (NP (DT These) (NNS elements)) (VP (VBP are) (VP (VBN separated) (PP (IN by) (NP (DT an) (NN air) (NN gap))))) (. .)))
These elements are separated by an air gap.
(ROOT (S (NP (NNP Air)) (VP (MD can) (VP (VB be) (VP (VBN separated) (PP (IN into) (NP (JJ several) (NNS elements)))))) (. .)))