Sentence:  One sample , which had been exposed to the atmosphere after evacuation at 375 ` C , showed the presence of adsorbed water ( about 0.3 wt % ) as evidenced by a weak resonance <WSD>line</WSD> which was very narrow at room temperature and which disappeared , due to broadening , at low temperature . 
Meaning of the word marked with <WSD> tags:  a mark that is long relative to its width