( ( The CAPILLARIES ) ( ( are ( ( the smallest ) ( of ( the ( blood vessels ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NNS CAPILLARIES)) (VP (VBP are) (NP (NP (DT the) (JJS smallest)) (PP (IN of) (NP (DT the) (NN blood) (NNS vessels))))) (. .)))
The CAPILLARIES are the smallest of the blood vessels.
(ROOT (S (NP (NNP Oxygen)) (VP (VBZ is) (VP (VBN transferred) (PP (IN through) (NP (NNS capillaries))))) (. .)))