5625
Twelve potential confounders were evaluated : habitat , organic enrichment , nutrients , deposited sediments , pH , selenium , temperature , lack of headwaters , catchment area , settling ponds , dissolved oxygen , and metals .
 Chemical: selenium; Chemical: oxygen
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: selenium; Chemical: oxygen