( ( ( A gram ) ( of ( ( protein or ) carbohydrate ) ) ) ( ( contains ( ( only four ) calories ) ) . ) )
(ROOT (S (NP (NP (DT A) (NN gram)) (PP (IN of) (NP (NN protein) (CC or) (NN carbohydrate)))) (VP (VBZ contains) (NP (QP (RB only) (CD four)) (NNS calories))) (. .)))
A gram of protein or carbohydrate contains only four calories.
(ROOT (S (NP (NP (CD One) (NN gram)) (PP (IN of) (NP (NNS carbohydrates)))) (VP (VBZ provides) (NP (NP (CD four) (NNS calories)) (PP (IN of) (NP (NN energy))))) (. .)))