Question

1. choose the correct answer.

which statement is true?

• burning fossil fuels puts oxygen in the air, which causes global cooling.
• burning fossil fuels puts carbon dioxide in the air, which has been tied to global warming.
• burning fossil fuels puts carbon dioxide in the air, which may cause global shrinking.
• burning fossil fuels puts oxygen in the air, which causes global warming.

1. choose the correct answer.

__ like buses and trains helps conserve energy by __.

• private transportation; adding pollution to the air
• public transportation; reducing the number of cars using fossil fuels
• private transportation; changing the type of pollution in the air
• public transportation; using more fossil fuels

Explanation:

Question 9

Fossil fuels (like coal, oil, gas) when burned, undergo combustion reactions. The general reaction for fossil fuel combustion (e.g., of methane \( \text{CH}_4 \)) is \( \text{CH}_4 + 2\text{O}_2
ightarrow \text{CO}_2 + 2\text{H}_2\text{O} \). This process releases carbon dioxide (\( \text{CO}_2 \)) into the atmosphere. Increased \( \text{CO}_2 \) (a greenhouse gas) traps heat, leading to global warming.

• Option 1: Burning fossil fuels does not put oxygen in the air (it consumes oxygen) and does not cause cooling. Eliminate.
• Option 2: Matches the science of fossil fuel combustion (releases \( \text{CO}_2 \)) and the link to global warming.
• Option 3: \( \text{CO}_2 \) does not cause "global shrinking"—the term is incorrect. Eliminate.
• Option 4: Burning fossil fuels consumes oxygen, not release it, and oxygen does not cause global warming. Eliminate.

Public transportation (buses, trains) reduces the number of individual cars on the road. Fewer cars mean less fossil fuel consumption (since each car burns fossil fuels, and consolidating passengers in public transit reduces total fuel use).

• Option 1: Private transportation (cars) increases pollution, not conserve energy. Eliminate.
• Option 2: Public transit (buses/trains) reduces car usage, so less fossil fuel is burned. Matches.
• Option 3: Private transportation does not conserve energy by changing pollution type. Eliminate.
• Option 4: Public transit aims to use less fossil fuel, not more. Eliminate.

Answer:

B. Burning fossil fuels puts carbon dioxide in the air, which has been tied to global warming.

Question 10