16421
For the case of one water molecule , most of the energy in the reactants region of the IRC is used for structural changes , while the transition state region encompasses the majority of electron activity , except for the formation of the C - O bond , which extends well into the products region .
 Chemical: C - O
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: C - O