page 08 9. The diagram shows apparatus used in an investigation to measure the rate of photosynthesis in Elodea (pondweed) at different wavelengths of light. Coloured filters were used to change the wavelength of the light. The volume of oxygen collected after 30 minutes was used to measure the rate of photosynthesis. bubbles of oxygen measuring cylinder scale (cm3) coloured filter lamp Elodea Suggested improvements to the investigation are shown. 1 Use a measuring cylinder with a narrower diameter. 2 Repeat the experiment several times and take averages. 3 Use a scale with more divisions. Which of these suggestions would improve the accuracy of the results? A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1, 2 and 3