题干
—— Show me the map, please. I wonder ______.—— Look, it's here, in the east of China, near Taiwan Province.
A：where is Diaoyu Island
B：where Diaoyu Island is
C：what is Diaoyu Island like
D：when Diaoyu Island is
答案(点此获取答案解析）
B
上的动点，点M到直线2x－y－a＝0（a为常数）的最短距离为
，则实数a的值为
