Which of the following statements about modified Hoagland solution is WRONG?
选项：

A:Nitrogen supplements as both ammonium and nitrate is beneficial to the plants because it promotes cation-anion balances within the plant.;
B:A chelating agent is added to maintain the availability of iron to the plants.;
C:The concentrations of mineral elements in the solution are much lower than those found in the soil around plant roots.;
D:None.