下列与我国地质灾害发生无关的因素是（    ）

如果把分式$\frac{xy}{x+y}$中的x、y的值都扩大5倍，那么分式的值 （　　）

This is part of a book's table of contents.

Chapter One: North America
The Fox and the Raccoon .....      1
Song of the Mountains .........      4
Little Feather Meets Bear .....       7
Chapter Two: South America
Kuma and the Big River.........     10
The Smallest Monkey ............    12
Three Tree Frogs ...................    15
Chapter Three: Africa
Marumbi Saves the Day.......        18
The Jumping Fish ................      22
Father Lion and His Son ......       25

–Yes, _______.

已知正方形ABCD中，S是所在平面外一点，连接SA，SB，SC，SD，AC，BD，在所有的10条直线中，其中异面直线共有（　　）