3715
Male Sprague - Dawley rats were exposed to either sham or IH ( cycles between 21 % O ( 2 ) / 0 % CO ( 2 ) and 5 % O ( 2 ) / 5 % CO ( 2 ) ) conditions for 7 h / day for 14 or 21 days .
 Chemical: O ( 2 ); Chemical: CO ( 2 ); Chemical: O ( 2 ); Chemical: CO ( 2 )
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: O ( 2 ); Chemical: CO ( 2 ); Chemical: O ( 2 ); Chemical: CO ( 2 )