( Bonds ( ( are one ) . ) )
(ROOT (S (NP (NNS Bonds)) (VP (VBP are) (NP (CD one))) (. .)))
Bonds are one.
(ROOT (S (NP (DT A) (JJ double) (NN bond)) (VP (VBZ consists) (PP (IN of) (NP (NP (CD one) (NN sigma) (NN bond)) (CC and) (NP (CD one) (NN pi) (NN bond))))) (. .)))