It’s politely requested by the hotel management that radios _____after 10 o’clock at night.

A．were not played

B．not to play

C．not be played

D．did not play

在人类生态学上，疾病与健康有关的三大因素是下列中的哪一项（）

A.患者、隐性感染者、健康者

B.患者、传播途径、社会因素

C.宿主、环境、病因

D.传染源、传播途径、易感性

E.生物学因素、心理因素、社会因素