抗日战争期间，日本军队在中国制造的一起大屠杀惨案，被中外舆论界称为人类“现代史上破天荒的残酷记录”“现代文明史上最黑暗的一页”，这起惨案发生在（     ）

我国疆域，许多大江大河源远流长。关于如图中两河说法正确的是（　　）

将50g质量分数为98%的浓硫酸稀释为20%的稀硫酸，需要加水的质量为（　　）

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”