7533
As the reduction of CO ( 2 ) proceeds through ET and then PT , the pyridine ring becomes aromatic , and thus Py catalyzes CO ( 2 ) reduction by stabilizing the PCET TS and the PyCOOH ( 0 ) product through aromatic resonance stabilization .
 CO ( 2 ), pyridine, CO ( 2 ), PyCOOH ( 0 )
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 CO ( 2 ), pyridine, CO ( 2 ), PyCOOH ( 0 )