2015的相反数为____ 

根据短文内容及首字母提示，填写所缺单词，使短文意思完整。每空限一词。
    Do you like your parents? They're two most i____people in your life. I think so. Because they're likely to influence you more than anyone e____ you have met and will meet. So if your dad worships a football team, s____ as Pittsburgh Steelers and Atlauta Falcons, you are likely to grow up being a big fan of a football team. And if your mom loves to r____ , you might grow up just carrying a book wherever you go, just a____she does.
    But parents do a lot more than just pass along their h____ . Moms and Dads need to care for their kids from the m____they're born. It's parents' task to love and guide kids---and most parents will do this as l____ as they live----even when the "kids" have g____up and have children of their o____ . That means you have many years ahead to share with your mom and dad.

一质量为m的物体放在动摩擦因数为$\mu$；的水平地板上，用一水平拉力作用于物体上使其获得加速度为a，欲使该物体加速度变为3a，应采取的正确办法是（   ）