猜想1：制造弹簧所用的材料可能影响弹簧的伸长量。

猜想2：弹簧的原长可能影响弹簧的伸长量。

猜想3：弹簧的粗细可能影响弹簧的伸长量。

小明为探究自己的猜想，设计出一个实验方案：

①将一根弹簧剪成长度不同的两根，测出两根弹簧的初始长度L₁、L₂。

②如图所示，固定弹簧的一端，用大小相同的力拉弹簧，测出两根弹簧的对应长度 、 。

改变拉力的大小，重复实验步骤①②，记录实验数据。

    Little Red Riding Hood lives near a forest (森林). She often goes to visit her grandma. She usually brings her some food. One day, when she is on her way to her grandma's home, a wolf sees her. The wolf stops her and asks, “Where are you going?” “My grandma's home.” answers Little Red Riding Hood. The wolf suggests (建议）picking some flowers for her grandma. The wolf runs to her grandma's home first. He eats the grandma. He is lying (躺）in the grandma's bed. Little Red Riding Hood comes and the wolf wants to eat her. Little Red Riding Hood cries for help. A hunter (猎人）comes quickly. The wolf is afraid, and he runs away.

2013年2月15日中午12时30分左右，俄罗斯车里雅宾斯克州发生陨石坠落事件．陨石在穿越大气层时摩擦燃烧，随后发生爆炸，以下说法中正确的是（　　）

我国内河运输最为发达的河流是（　　）