( ( In ( conditions ( where ( ( no ( free oxygen ) ) ( is present ) ) ) ) ) ( , ( ( anaerobic respiration ) ( ( takes place ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (NP (NNS conditions)) (SBAR (WHADVP (WRB where)) (S (NP (DT no) (JJ free) (NN oxygen)) (VP (VBZ is) (ADJP (JJ present))))))) (, ,) (NP (JJ anaerobic) (NN respiration)) (VP (VBZ takes) (NP (NN place))) (. .)))
In conditions where no free oxygen is present, anaerobic respiration takes place.
(ROOT (S (NP (JJ Anaerobic) (NN respiration)) (VP (VBZ occurs) (SBAR (IN if) (S (NP (NN oxygen)) (VP (MD can) (RB not) (VP (VB be) (VP (VBN obtained) (PP (IN at) (NP (DT a) (JJ sufficient) (NN rate))))))))) (. .)))