( ( Fields ( ( ( of ( ( ( magnetism , ) ( of gravity ) ) , ) ) and ) ( of ( other forces ) ) ) ) ( ( create ( complex interplay ) ) . ) )
(ROOT (S (NP (NP (NNP Fields)) (PP (PP (IN of) (NP (NP (NN magnetism)) (, ,) (PP (IN of) (NP (NN gravity))) (, ,))) (CC and) (PP (IN of) (NP (JJ other) (NNS forces))))) (VP (VBP create) (NP (JJ complex) (NN interplay))) (. .)))
Fields of magnetism, of gravity, and of other forces create complex interplay.
(ROOT (S (NP (NNP Gravity) (CC and) (NNP magnetism)) (VP (VBP are) (NP (DT both) (JJ common) (NNS forces))) (. .)))
Gravity and magnetism are both common forces.