21237
Generated toxicophore models showed four important features responsible for basal cytotoxicity : ( i ) two hydrophobic aliphatic groups ( HYD Aliphatic ) , ( ii ) ring aromatic group ( RA ) and ( iii ) hydrogen bond donor ( HBD ) .
 Chemical: hydrogen
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: hydrogen