GRE Text Completion: JiJing 1373-GRE填空机经1373题 - BZLFVU22_736FHP5A

In the early 1990s, the discovery of a new microbe in wastewater led microbiologists to (i)____________ ammonia's conversion to nitrogen compounds. Called anammox (for anaerobic ammonia oxidation), the microbe was converting into nitrogen gas in the absence of oxygen, a reaction previously assumed to be (ii)____________. A. question existing dogma about B. hazardous C. abandon efforts to facilitate D. irreversible E. raise health concerns regarding F. impossible