填一填
____
I ______ go to bed______ my mother came back home.
若定义运算:a⊗b= {a,(a≥b)b,(a<b) ,例如2⊗3=3,则下列判断中错误的是____
①a⊗b=b⊗a;
②a⊗(b⊗c)=(a⊗b)⊗c;
③(a⊗b)2=a2⊗b2
④c•(a⊗b)=(c•a)⊗(c•b)(c>0)