请教一道英语填空题,谢谢!

问题描述:

请教一道英语填空题,谢谢!
这是关于涉及到UFO的一小段填空题:
Radio stations and the police are often swamped _______ when something _______ is seen in the skies. Once an explanation is given, most people are happy to believe it. But some people are hard to convince. Are the authorities really telling the truth, or do they _____ something they aren't telling anyone else?

with calls
unidentified,(wired or strange)
hide,(或者 cover)
不完全确定,不过感觉也算通顺.