( Humans ( ( have ( ( ( only 23 ) pairs ) ( of chromosomes ) ) ) . ) )
(ROOT (S (NP (NNS Humans)) (VP (VBP have) (NP (NP (QP (RB only) (CD 23)) (NNS pairs)) (PP (IN of) (NP (NNS chromosomes))))) (. .)))
Humans have only 23 pairs of chromosomes.
(ROOT (S (NP (NNS Humans)) (VP (VBP have) (NP (NP (CD 23) (JJ pairs) (NNS pairs)) (PP (IN of) (NP (NNS chromosomes))))) (. .)))