A:铁
B:碳
C:氧
D:钙
先化简: (x−xx+1)÷(1+1x2−1) ,然后在-1,0,1,2四个数中选一个你认为合适的数代入求值.
阅读理解,判断正误。
I'm Lily. I like animals.Look! This is a panda. It's fat. It has two black eyes. But that rabbit has two red eyes. I have a cat. It has two green eyes. I have blue eyes.