Which of the following statements(s) is/are incorrect regarding the s-block elements? I. Francium is highly radioactive element. II. Oxides and hydroxides of alkali metals and alkaline earth metals are not alkaline in nature. III. Sodium and potassium are the only two s-block elements are found in large proportion in biological fluids. IV. Biological function of s-block elements is due to maintenance of ion balance and nerve impulse condition.