Reportedly yesterday a group of American soldiers were walking along the road in Irap when a bomb was ______ .

A．set out

B．set about

C．set off

D．set up

《旅游投诉暂行规定》第十五条规定，旅游投诉管理机关接到（），经审查不符合规定受理条件的，应当在（）日内通知投诉者不予受理。