A

    Our eyes are very important to us. They are like cameras. We can 1 with our eyes. But if we don't take care of them, they may get hurt. 2 can we protect our eyes?

    On 3 days when the sun shines brightly, we'd better wear sunglasses. When we 4, we shouldn't stay too close to the books and the light shouldn't be too bright or too dark. We shouldn't read in bed. It's bad for our 5. We mustn't play games too long on computers or on mobile phones.

如图是探究电流通过导体产生的热量与什么因素有关的实验装置，将两根阻值不等的电阻丝R₁、R₂串联后分别放入两个透明容器中，并封闭等量的空气，通电前，A、B两U形管内的液面相平，接通电源一分钟后，通过R₁、R₂的电流分别为I₁、I₂，则（　　）

函数$y=\left(a-2\right)x^{a^2-2}$是反比例函数，则a的值是____ 　．