如图甲，木块从斜面匀速滑下时，受到摩擦力大小为F₁；当用平行于斜面的推力将该木块由斜面底端匀速推至顶端的过程中，推力大小为F₂（如图乙），关于F₁与F₂的大小关系和能量的变化，下列说法中正确的是（　　）

观察蚯蚓、沙蚕和水蛭的图片，它们都有共同的特点，属于（　　）

    Hello! I'm Victor.I have a bed, a desk, two chairs and a computer in my bedroom.My bed is small but very nice.It's blue because I like blue very much.My desk is big.It's white.You can see a computer and so many books on it.I do my homework here.I have two chairs.One is big and one is small.The big one is near the bed.The small one is near the window.I like my room.