阅读下面的短文，根据短文内容完成句子。每空词数不限。

    This is a song millions of Americans will hear this New Year's Eve. It is called “Auld Lang Syne(《友谊地久天长》)”. It is the traditional music played during the New Year's celebration. Auld Lang Syne is an old Scottish poem. It tells about the need to remember old friends.

    The words “auld lang syne” means “old long since”. No one knows who wrote the poem first. However, a version (译本) by Scottish poet Robert Burns was published in 1796. The words and music we know today first appeared in a songbook three years later.

    The song is played in the United States mainly on New Year's Eve. The version you are hearing today is by the Washington Saxophone Quartet. As we end our program with “Auld Lang Syne”, I would like to wish all of our radio friends a very Happy New Year! This is Buddy Thomas.

物理学家和数学家牛顿曾提出了物体在常温环境下温度变化的冷却模型，如果物体的初始温度为θ₁℃，空气温度为θ₀℃，则tmin后物体的温度f（t）满足：f（t）=θ₀+（θ₁﹣θ₀）•e^﹣kt（其中k为正的常数，e=2.71828…为自然对数的底数），现有65℃的物体，放在15℃的空气中冷却，5min以后物体的温度是45℃．

（Ⅰ）求k的值；

（Ⅱ）求从开始冷却，经过多少时间物体的温度是25.8℃？

（Ⅲ）运用上面的数据，作出函数f（t）的图象的草图．

基流是地下水补给进入河水中的部分，其径流量较为稳定，为河川的基本流量；它在维持河道生态、提供枯水季节供水中作用显著。基流指数是基流占河流径流的比重。下表为40年间黄河源区(位于青藏高原)的相关数据。根据表中数据的相关性判断，黄河源区河流径流量大小主要取决于(    )