已知AB是⊙O的直径，弧AC的度数是30°．如果⊙O的直径为4，那么AC2等于

题干

已知AB是⊙O的直径，弧AC的度数是30°．如果⊙O的直径为4，那么AC²等于（　　）

A：2- $\sqrt{3}$

B：4 $\sqrt{3}$ -6

C：8-4 $\sqrt{3}$

D：2

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C

Welcome to Wenzhou Zoo! There are many different kinds of animals in the zoo．They come from different countries and they eat different food.

	Beibei is a cute panda．She is five years old from China. She is black and white．She likes eating bamboo and drinking water．
	Martin is a big elephant．He is ten years old with a long nose．He likes eating grass. People can teach* him to do much work to help them．
	Dudu is a monkey. He is two years old from Japan．He likes eating bananas and cakes．He often lives in the trees．
	Nick is a lion. He is strong．He is nine years old from England．He likes eating meat. He is very happy in the zoo．