( ( ( ( ( The cathode ) , ) ( ( at which ) ( reduction ( is ( taking place ) ) ) ) ) , ) ( ( ( is ( the ( ( most positive ) electrode ) ) ) ( so ( ( the cathode ) ( is ( written ( on ( the right ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN cathode)) (, ,) (SBAR (WHPP (IN at) (WHNP (WDT which))) (S (NP (NN reduction)) (VP (VBZ is) (VP (VBG taking) (NP (NN place)))))) (, ,)) (VP (VBZ is) (NP (DT the) (ADJP (RBS most) (JJ positive)) (NN electrode)) (SBAR (IN so) (S (NP (DT the) (NN cathode)) (VP (VBZ is) (VP (VBN written) (PP (IN on) (NP (DT the) (NN right)))))))) (. .)))
The cathode, at which reduction is taking place, is the most positive electrode so the cathode is written on the right.
(ROOT (S (NP (NP (DT The) (NN electrode)) (SBAR (WHPP (IN at) (WHNP (WDT which))) (S (NP (NN reduction)) (VP (VBZ occurs))))) (VP (VBZ is) (VP (VBN called) (NP (DT the) (NN cathode)))) (. .)))