人体每天消耗的能量来自营养素，营养素包括糖、蛋白质、维生素、无机盐和水。
参考答案：对
—I can’t get on with some of my classmates. They just leave me in the cold.
—______ But what’s the reason?
A．Sorry to hear that.
B．How about that?
C．Don’t mention it.
D．Never give up.
如图所示，用轻绳将重球悬挂在竖直光滑墙上，当悬绳变长时，下列说法正确的是
A．绳子拉力变大
B．绳子拉力变小
C．墙对球的弹力变大
D．墙对球的弹力变小
