方程组$\left\{\begin{array}{c}x+y=2\\ 2x+2y=3\end{array}\right.$没有解，因此直线y=﹣x+2和直线y=﹣x+$\frac{3}{2}$在同一平面直角坐标系中的位置关系是（　　）

    Today is Children's Day.The students are in the park.There's a hill and a lake in the park.Now it's lunchtime.They're having a picnic on the grass.Zhang Tao is having a hamburger,Li Ming is eating a hot dog, Wang Lan is drinking some orange juice.They are going to to go skating after lunch.They can't find Su Hai and Su Yang.Oh,they're flying kites over there.All the students are very happy.

召开2001年APEC(亚太经合组织)会议的城市是(     )

在边长为a的等边三角形ABC中，AD⊥BC于D，沿AD折成二面角B﹣AD﹣C后，BC=$\frac{a}{2}$，这时二面角B﹣AD﹣C的大小为____ ．