世界人口稠密区绝大部分分布在(  )

   Once there was a king. He liked to write stories. He thought his stories were good, so he like to show them to people. As people were afraid of him, they all said his stories were very good. One day, the king showed some of his best stories to a famous writer. He wanted the writer to praise(赞美)these stories. But the writer said his stories were so bad that he should throw them into the fire. The king got very angry and sent him to prison(监狱). After some time, the king set him free and ordered him to come to his palace(宫殿). Again he showed some of his new Stories and asked what he thought of them. After reading them, the writer at once turned to the soldiers and said, "Take me back to the prison."

Ann ____ (go) to the bookstore（书店）last Sunday, then ____ I (carry) them on my bike.

某人向正东方向走xkm后，然后沿着西偏南30°方向走了3km，结果他离出发点为$\sqrt{3}$km，那么x的值为（　　）