which, who, whom, what, where, whenThe treatment, 1 is being tried by researchers at four hospitals, has helped patients 2 have failed to respond to other remedies.
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  • 2、
【正确答案】 1、正确答案：which,    2、who    
【答案解析】解析：第一空的先行项是the treatment且在关系分句中作主语，因此引导词应为which。第二空的先行项是patients且在关系分句中作主语，因此引导词应为who。答案为which，who。