Explain about blackmans law of limiting factors​

Which of the following is an oxidation-reduction reaction? (pictured below)

Which of the following represents the chemical reaction of hydrazine and hydrogen peroxide to produce nitrogen and water? a. nitrogen + hydrogen peroxide → hydrazine + water b. nitrogen + water → hydrazine + hydrogen peroxide c. hydrazine + hydrogen peroxide → nitrogen + water d. water + hydrogen peroxide → nitrogen + hydrazine

Which step is not included in the step approach to calculating the greatest common divisor?