Sentence:  It was approximately one month before the belt problem was noticed and corrected , but at no time was there a deficiency of dissolved <WSD>oxygen</WSD> . 
Meaning of the word marked with <WSD> tags:  a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust