Correct answer: (3) recycling aluminum

Aluminum recycling is the process in which scrap aluminum is reused after its primary production. Aluminum is the most abundant metal in the earth's crust. However, a great amount of energy is required to extract it from ore. Thus, when aluminum is recycled, a lot of energy is saved, as well as the aluminum deposits in the crust.

Incorrect answers:

(1) deforestation

Deforestation is the removal of trees from the forest due to agricultural practices or urbanization. Although trees are considered as renewable resources, it takes years for trees to grow and replace those that are cut.

(2) removing carnivores from a forest

If carnivores are removed in the forest, there would be an ecological imbalance because they are important in the transfer of energy from one group of organism to another.

(4) heating homes with fossil fuels

Correct answer: (2) reducing the human population

Reducing the human population would do not harm to the lives of endangered species. It could be beneficial to them in so many ways. The major causes of the endangerment of species are habitat destruction, introduction of exotic species, and overexploitation. These factors are all effects of the increased human activity due to an increase in human population. For instance, wildlife habitats are disturbed when areas of land are developed into subdivisions or used to build factories. Or, humans bring exotic species to a new location where there could be few predators for those exotic species. Thus, the exotic species compete with the existing species-and since there are few predators, the exotic species replace the existing species that are in the same niche with the exotic species.

Incorrect answers:

(1) releasing more carbon dioxide into the atmosphere

Releasing more carbon dioxide in the atmosphere would cause greenhouse effect, and thus, climate change. This impacts the whole biosphere, most especially the endangered species.

(3) decreasing the amount of dissolved oxygen in the oceans

Decreasing the amount of dissolved oxygen in the oceans will harm the endangered species especially those that inhabit the ocean. Aquatic animals take in dissolved oxygen during respiration.

(4) reducing the thickness of the ozone layer

Correct answer: (2) Many people care more about their personal comforts than about the possible effects of global warming.

Based on the answers of the respondents, they were more concerned about personal matters such as taxes and gasoline expenses, than preventing global warming. For instance, the answer to the second question states that they prefer using big cars simple because they like it and they think it is safer for them. They do not consider the use car with better fuel economy to lessen the gas emissions that contribute to global warming.

Incorrect answers:

(1) Many people are very aware of the possible effects of global warming.

The answer to the last question clearly states that people are not informed about global warming. They do not know that the changes in climate are caused by several human activities and inventions.

(3) Many people are willing to sacrifice to reduce the possible effects of global warming.

This is not true based on the answers to the interview. They are more concerned about their taxes or gasoline expenses than contributing in the alleviation of climate change.

(4) Many people are now taking action to reduce the possible effects of global warming.

Correct answer: (4) an increased demand for land use

Among the choices given, this is the only possible result of increasing population. More population would mean more land to build houses on, more land to produce crops for food, and more land to build infrastructures necessary for producing materials for human use, such as clothing.

Incorrect answers:

(1) a decreased demand for deforestation

As population increases, more trees are necessary to produce paper, clothing, and other materials for human use that are made up of timber and its by-products.

(2) an increase in available fresh water

As population increases, more fresh water is needed for human consumption and other activities such as bathing, washing of clothes and dishes, etc.

(3) a decrease in air pollution

Correct answer: Biofuel crops

Biofuels are alternative fuels that come from plants and plant-derived sources. Biofuels are usually used for transportation. One such of biofuel is called the bioethanol, which can be used as substitute for petrol. It is produced by fermenting cellulose from corn (maize) and sugar cane. Another type of biofuel is the biodiesel, which can be sourced from oil crops like rapeseed, palm, and soybean.

Biofuel crops are considered as a renewable source of energy because it can be easily replaced (by planting the crops) in a relatively short span of time.

Biofuels are carbon-neutral: the carbon dioxide released during combustion is initially extracted from the atmosphere during photosynthesis, thus there is zero net greenhouse gas emissions.

Biofuels also contributes to the reduction in the release of volatile organic compounds, as the addition of ethanol gasoline oxygenates the fuel mixture so it burns more completely. Ethanol also rids the use of harmful lead.

Since biofuels come from plants, they are biodegradable and non-toxic. Thus, biofuel spillages are not as harmful as fossil fuel spillages.