定义运算a⊗b=a（b﹣1），下面给出了关于这种运算的四个结论：①2⊗（﹣1）=﹣4；②a⊗b=b⊗a；③若a+b=1，则a⊗a=b⊗b；④若b⊗a=0，则a=0或b=1．其中正确结论的序号是（　　）

单词拼写
(1)I called you last night but you didn't answer me. What was h____ .
(2)I looked for my cat e____ , but I didn't find it.
(3)He is good at math, but he failed the exam this time. I can not i____  how strange it is.
(4)Both Tom and Tim have t____ to the ball game. They’ll go and watch it.
(5)Liu Yang becomes a national h____  because she is the first Chinese woman that has been to the space.
(6)Lily m____  her English teacher while she was shopping in the mall.
(7)There are still lots of p____  families in China. We should help them.
(8)This problem is too s____ . Even a kid can work it out.
(9)I had a car accident yesterday. L____ , there was nothing wrong with me.
(10)Do you make the bed for your parents?  No, they make the bed by t____ .

读图区域等高线地形图，下列判断正确的是（    ）