這符號有何意思？(難度：９)

This is another of the earliest ideograms used by humans in this cycle of civilization. It was associated with the idea of divinity and power. Later,
圖片參考：http://www.symbols.com/pics/small/26/2624.gif
is more common for that purpose in Christian art.
This sign has also been used as an anti-Semitic symbol (compare with
圖片參考：http://www.symbols.com/pics/small/26/2612.gif
is used as a halo in Buddhism it is usually yellow or orange.) There was instructions as to how the yellow ring was to be worn worked out, for example, in Reichstadt Frankfurt in 1452.
A few modern uses of this sign: calm in meteorology, temporary runway in aviation, and here they give you food and money in the British and Swedish systems of hobo signs.
http://www.symbols.com/encyclopedia/26/2611.html