A:3a-b
B:a÷3-b
C:(a+b)÷3
D:(a-b)÷3
选项
物质
A
B
C
D
X
Fe2O3
CaCO3
Cu
Y
Fe
CO
CaO
CuO
Z
FeCl2
CO2
Ca(OH)2
Cu(OH)2
Watching TV too much is bad for our____(眼睛).