( ( Some ( of ( ( the topics ) ( we ( have ( discussed ( so far ) ) ) ) ) ) ) ( ( are ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( air pollution ) , ) ( ozone depletion ) ) , ) ( global warming ) ) , ) ( ( energy sources ) ( both ( ( renewable and ) non-renewable ) ) ) ) , ) ( acid rain ) ) , ) ( water quality ) ) , ) ( nuclear energy ) ) and ) nutrition ) ) . ) )
(ROOT (S (NP (NP (DT Some)) (PP (IN of) (NP (NP (DT the) (NNS topics)) (SBAR (S (NP (PRP we)) (VP (VBP have) (VP (VBN discussed) (ADVP (RB so) (RB far))))))))) (VP (VBP are) (NP (NP (NN air) (NN pollution)) (, ,) (NP (NN ozone) (NN depletion)) (, ,) (NP (JJ global) (NN warming)) (, ,) (NP (NP (NN energy) (NNS sources)) (ADJP (DT both) (JJ renewable) (CC and) (JJ non-renewable))) (, ,) (NP (JJ acid) (NN rain)) (, ,) (NP (NN water) (NN quality)) (, ,) (NP (JJ nuclear) (NN energy)) (CC and) (NP (NN nutrition)))) (. .)))
Some of the topics we have discussed so far are air pollution, ozone depletion, global warming, energy sources both renewable and non-renewable, acid rain, water quality, nuclear energy and nutrition.
(ROOT (S (NP (NNP Air) (NN pollution)) (VP (VBZ causes) (NP (NP (JJ acid) (NN rain)) (, ,) (NP (NN ozone) (NN depletion)) (, ,) (CC and) (NP (JJ global) (NN warming)))) (. .)))