The correct answer is statement B.
The UV rays refer to the radiation emitted from the Sun, which the Earth receives. These radiations exhibit a direct influence on human skin, these possess the tendency to produce mutations in human genome and are carcinogenic in characteristic.
A lightweight substance can be examined in controlled natural environments with the application of natural UV light, like the skin cells that can be observed under two conditions, that is, in controlled condition, in which a skin cell is coated with lightweight material, and in experimental condition, in which skin cell is coated with lightweight substance.
After exposing these cells to distinct ranges of UV rays, it will assist in finding an important conclusion considering the benefit of the lightweight substance in obstructing sunlight. The controlled cell will die as it is not able to withstand UV rays, while the experimental skin cell will either die or survive.
In case, if it thrives then it can be deduced that the lightweight substance is efficient in preventing ultraviolet rays, and if it dies, then a lightweight substance is not efficient in preventing UV rays.
Thus, testing the substance in a controlled natural setting by utilizing UV light, and measuring the UV light passing through would be the most appropriate approach for examining the substance.