21210
While the basic nanofibrous morphology is retained in all cases , selection of the particular core residues results in switching from antiparallel hydrogen bonding to parallel hydrogen bonding in addition to changes in nanofiber morphology and in hydrogel rheological properties .
 Chemical: hydrogen; Chemical: hydrogen
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, hydrogen 
Answer:
 Chemical: hydrogen; Chemical: hydrogen