When the audience heard the alarm, they all hurried to        they thought was an emergency exit door.[ ]

A. what    

B. which    

C. where      

D. who

甲、乙两医生用各自发明的药物，治疗甲肝，甲治疗5例，全部治愈，乙治疗10例，治愈8例，则

A．两药治愈率，甲药可表示为100%

B．甲药比乙药治愈率高

C．乙药比甲药治愈率高

D．比较疗效需做假设检验

E．本资料无法比较两药疗效