27099
We found that under conditions where virtually no subsurface hydrogen species are present , the HD formation rate can be described exceptionally well by a classic Langmuir - Hinshelwood model .
 Chemical: hydrogen; Chemical: HD
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: hydrogen, HD 
Answer:
 Chemical: hydrogen; Chemical: HD