( They ( inconsistently ( ( identify ( forces ( in ( nature ( -LRB- ( ( ( e.g. , ) ( gravity ( , ( magnetism ( , friction ) ) ) ) ) -RRB- ) ) ) ) ) ) . ) ) )
(ROOT (S (NP (PRP They)) (ADVP (RB inconsistently)) (VP (VBP identify) (NP (NP (NNS forces)) (PP (IN in) (NP (NP (NN nature)) (PRN (-LRB- -LRB-) (NP (NNP e.g.)) (, ,) (NP (NN gravity) (, ,) (NN magnetism) (, ,) (NN friction)) (-RRB- -RRB-)))))) (. .)))
They inconsistently identify forces in nature (e.g., gravity, magnetism, friction).
(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.