A:2 3 +3 3 =5 6
B:( 2+1 )(1﹣ 2 )=1
C:(xy)﹣1( 12 xy)2= 14 xy
D:﹣(﹣a)4÷a2=a2
下列属于东西走向的山脉是( )
It's very useful to ______the correct answers next to the mistakes.