Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42 LIGHT POLLUTION Light pollution is an excessive, wasteful and obstructive light resulting from human activities. It is mostly seen in densely-populated cities and industrialized areas. The pollution includes the light used in factories and office buildings, commercial properties, streetlights, illuminated sporting venues and infrastructure. ...

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42

LIGHT POLLUTION

Light pollution is an excessive, wasteful and obstructive light resulting from human activities. It is mostly seen in densely-populated cities and industrialized areas. The pollution includes the light used in factories and office buildings, commercial properties, streetlights, illuminated sporting venues and infrastructure. As beneficial as the invention of light and the development of industrialization have been to mankind, their secondary effect, light pollution, is adverse in multiple ways.

The two main types of light pollution recognized by environmentalists are light that intrudes on a natural setting and the use of disproportionate amount of light indoors. Light pollution may also be defined according to very specific categories into light trespass, glare and clutter. Light trespass happens when unwanted light enters someone’s property. For example, a neighbor turns on a bright light in his yard and this light enters a neighboring bedroom window, causing sleep deprivation or obstructing an evening view. Glare is the extreme contrast between light and dark areas such that the human eye has difficult in adjusting. Glare is not merely annoying, but bright lights on dark roads can obscure night vision for motorists temporarily, with accidents sometimes being the result. Clutter is the presence of numerous groups of lights. It may produce confusion and distract viewers. Badly designed street lights and neon advertising signs come under this category.

Even a small amount of light pollution can have a negative influence on its surrounding. For the novice astronomer, a little light can make it difficult to observe the night sky; this is the reason observatories are located in areas where light emissions are forbidden. For the human body, excessive light is detrimental. Ailments such as headaches, fatigue, stress, high blood pressure and anxiety are common to those who are constantly exposed to light. The effects of light pollution on animals are just devastating. Birds that migrate to the south for the winter are disoriented by lights on tall buildings, and they are sometimes attracted to these lights: millions die when they collide with these buildings. Zooplankton is unable to rise to the surface of a water body to eat algae because of bright light; the algae blooms overgrow, killing off other plants and destroying the water quality. The circadian rhythm of reptiles, insects and other animals is affected when light keeps them awake.

Although the United States government is aware of the problem, it has been a challenge to draw up and enforce lighting regulations for the entire country. Some cities have formulated their own standards and solutions regarding outdoor lighting, but on the whole, the same standards cannot be administered in every city. Some solutions include minimizing the use of light, using timers to turn off lights automatically, utilizing the most pertinent types of light, redesigning plans and using sodium light which emits a single wavelength of light that is easier to filter

The word “their” in the passage refers to ______