( ( Natural gas ) ( ( ( is ( a ( nonrenewable resource ) ) ) ( because ( it ( ( can not ) ( be ( replenished ( on ( a ( human ( time frame ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Natural) (NN gas)) (VP (VBZ is) (NP (DT a) (JJ nonrenewable) (NN resource)) (SBAR (IN because) (S (NP (PRP it)) (VP (MD can) (RB not) (VP (VB be) (VP (VBN replenished) (PP (IN on) (NP (DT a) (JJ human) (NN time) (NN frame))))))))) (. .)))
Natural gas is a nonrenewable resource because it cannot be replenished on a human time frame.
(ROOT (S (NP (JJ Nonrenewable) (NNS resources)) (VP (MD can) (RB not) (VP (VB be) (VP (VBN replaced) (ADVP (ADVP (RB as) (RB easily)) (SBAR (IN as) (S (NP (PRP it)) (VP (VBZ is) (VP (VBN consumed))))))))) (. .)))