阅读下列短文,从每小题所给的A、B、C、D四个选项中选出一个最佳选项。

EASTGATES  YANGZHOU

Rollerworld is a public skating rink（旱冰场）that welcomes everyone from beginners to experts.

NOTICE

— under 12's must be taken care of by an adult.

— small cost for adults watching children

— no dirty or dangerous skates

— dress must be neat

— no jackets, hats or open clothing to be worn

— no newspapers, books, magazines, games allowed in Roller Café or Roller Bar

— no smoking except in Roller Bar and smoking room of Roller Café

— over 18's only in Roller Bar

“Roller skating fun for everyone”

“学习就像爬山。爬过这一座山头，还有另一座更高的山，永无终点。”这句话主要告诉我们学习是义务和责任。（   ）

如图，轻绳OA一端系在天花板上，与竖直方向夹角37°．轻绳OB水平，一端系在墙上，结点O处挂一重为40N的物体．

若方程x²﹣3x﹣4=0的两根分别为x₁和x₂，则$\frac{1}{x_1}+\frac{1}{x_2}$的值是（　　）