Today is Saturday. In the morning, Xiaoyong is sleeping, but the phone rings. He wakes up from his dream. He gets up and goes to the park near his home. He is doing exercise, but it starts to rain. He has to go home. He is doing his homework at home, but the bell rings.

    In the afternoon, Xiaoyong is riding his bike, but suddenly(突然)a little dog runs to him. He falls off his bike. He is so sad.

农田中除去杂草是为了合理调整生态系统中的能量流动关系，使能量持续高效地流向____ 的部分．

2012年6月21日民政部发布公告，宣布国务院批准撤销海南省西沙群岛、南沙群岛、中沙群岛办事处，设立地级市三沙市，下辖西沙、南沙、中沙诸群岛及海域（如图）。

三沙市所在省级行政区的简称是（   ）