如图，△ABC≌△ADE，∠DAC=60°，∠BAE=100°，BC、DE相交于点F，则∠DFB的度数是（　　）

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    I used to go ____ with my mum on clear nights and look at the sky. It looked like black velvet with a million ____ on it. In different seasons, we saw different groups of stars. Sometimes we saw stars ____ brightly ____ the sky. How beautiful they were!

    Studying the stars was great ____ for me. Once I learnt a little about them, I soon wanted to find out more and more. Now it is my ____. I host a TV program ____ The Sky at Night. I use my knowledge to tell people about the stars in a ____ way. I am proud of my TV program me—it has ____ for more than 50 years!

如图，圆O过点B、C，圆心O在正△ABC的内部，AB=2$\sqrt{3}$，OC=1，则圆O的半径为（　　）