A:2x2﹣x2=1
B:5xy﹣4xy=xy
C:2m2+3m3=5m5
D:5c2+5d2=5c2d2
配平方程式:
____ C2H2+____ O2____ CO2+____ H2O
____ Fe2O3+____ CO____ CO2+____ Fe.
— Why are you going to the gift shop?
— Because l want to buy a present for my mother today.