Which is not balanced A) NO2 + H2O> HNO3, B) CO2+H2O> H+ + HCO3-

C) CaCO3 = 2HCL > CaCL2 + H2O + CO2
D) 2 03 > 3 02
is it B and D or something else how do I tell please

A isn't balanced, there are two hydrogen atoms on the left and only one on the right.

The others are balanced (though there's a typo in reaction C). A balanced reaction has the same number of atoms of each element on both sides of the reaction, and the total charge has not changed.