Which of the following statement is incorrect ?

The standard enthalpy of reaction is the enthalpy change for a reaction when all the participating substances are in their
standard states

The enthalpy of an element in its standard state is zero

The enthalpy of CO_2(g) at 298K and 1 bar is zero

Standard conditions are denoted by adding the superscript to the symbol $∆\mathrm{H}$ e.g.,$∆{\mathrm{H}}^0$