"Spy balloons" - What's going on?

Available for over a year

On the 4th February the US shot down a suspected Chinese spy balloon and since then, three other "unidentified objects" have been downed across North America. The FBI are in the process examining some of the items - but what are they? And should we be worried about what's happening? The BBC's North America Correspondent Nomia Iqbal has the answers to five key questions.