15. What is/are true for substance and mixture? 1. Pure substance melts completely. II. Pure substance has a varying boiling point. III. Mixture does not melt completely. IV. Mixture has a fixed boiling point. A. I and II only B. I and III only C. II and IV only D. I and IV only 16. A pinch of bread was placed inside a test tube and heated until it became blackish in color and released some gas. Which of the following statement/s is/are true according to the given information? 1. Bread is solution, II. Bread is composed of only one substance. III. Bread is made up of solid and gaseous substances. IV. Bread is made up of mixtures of different substances, A. I only B. II & III C. II only D. III & IV 77 77 Turbo lice​