Answer:
b) Blue
Step-by-step explanation:
The color of light reflecting on plants tend to to affect photosynthesis (how the plants produce their food). Plants needs all visible colors of light except green. Plants react in different ways to different colours of light they are exposed to. The red light helps plants but only helps then to grow flowers, the yellow colour is not ideal because it will do little to protect from heat due to too much light. But the blue colour helps in good vegitative growth of the leaves and it also does a good job in absorbing heat.
Since the gardner wants to shade her plants with coloured transluscent plastic sheets, the ideal plastic sheet colour will be blue, because blue is a good absorber of heat and it also does tremendously well in the vegetation of plants.