Explanation:
E When a red coloured object is illuminated by a mercury vapour lamp, it will reflect combination of red, green, and blue light. However, when it is seen through a green filter, the filter will only allow green light to pass through and block other colors of light.
Since red light is blocked by the green filter, the only remaining colors that reach our eyes are green and blue. Therefore, the red object will appear dark, almost black, when seen through a green filter illuminated by a mercury vapour lamp.