Sentence:  Analysis of the ethane fraction also revealed anomalous deuteration of the ethane, the <WSD>ethanes</WSD> C<sub>2</sub>H<sub>5</sub>D, C<sub>2</sub>H<sub>4</sub>D<sub>2</sub> and C<sub>2</sub>H<sub>3</sub>D<sub>3</sub> being observed as well as C<sub>2</sub>H<sub>6</sub>. <WSD>Ethanes</WSD> with more than three D atoms were not detected. 
Meaning of the word marked with <WSD> tags:  The same compound, subjected to modification by replacing one or more of the hydrogen atoms with other radicals.