题干
Your parents will ________ at four o'clock this afternoon.
A：arrive at
B：get to
C：reach
D：arrive
答案(点此获取答案解析）
D
+y2=1交于P1，P2两点，线段P1P2的中点为P，设直线m的斜率为k1(k1≠0),直线OP的斜率为k2 ,则k1k2的值为…( )