10845
The strong and direct evidence is derived by the observation of through - space couplings , such as , ( 1h ) J ( FH ) , ( 1h ) J ( FN ) , and ( 2h ) J ( FF ) , where the spin polarization is transmitted through hydrogen bond .
 FH, FN, FF, hydrogen
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 FH, FN, FF, hydrogen