Elizabeth Blackwell, the first woman medical doctor in the United States, founded the New York Infirmary, an institution that have always had a completely female medical staff.
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【正确答案】 1、正确答案：have—has    
【答案解析】解析：考查主谓语一致。that引导的定语从句修饰先行词an institution，从句主语that指代单数意义的institution，故其谓语也应用动词的单数形式，have应改为has。