下列函数是二次函数的是(        )

将质量均为M=1kg的编号依次为1，2，…6的梯形劈块靠在一起构成倾角α=37°的三角形劈面，每个梯形劈块上斜面长度均为L=0.2m，如图所示，质量m=1kg的小物块A与斜面间的动摩擦因数μ₁=0.5，斜面与地面的动摩擦因数均为μ₂=0.3，假定最大静摩擦力与滑动摩擦力相等．现使A从斜面底端以平行于斜面的初速度v₀=4.5m/s冲上斜面，下列说法正确的是（   ）

    Who says dogs don't need to wear beautiful clothes? My dog Michael has many different kinds of1, and he likes them a lot. Look at him in the picture! He is2 a grey hat, a yellow shirt and red shoes today. And he also wears a3 of sunglasses. You look so4, Michael! I design clothes for Michael.It takes me a lot of free time, 5 I enjoy it. All of Michael's clothes are made 6good cotton. And they 7 him very well. Every time I take Michael out for a 8 in the park, I can hear people saying, “Oh, look at that dog. How fashionable he looks!” I'm very happy about it. It 9 that Michael is already a star. Walk for today, Michael. What? You want to play with the ball? All right, let's go! Oh, 10me! I'm putting on my sneakers.