The greenhouse effect, which leads to global warming and climate change, is mainly caused or intensified by which of the following human activities and factors?

Introduction / Context:
The greenhouse effect is a natural process in which certain gases in the atmosphere trap heat and keep the Earth's surface warm enough to sustain life. However, human activities have significantly intensified this effect, leading to global warming and climate change. Examinations frequently ask about the main causes of this enhanced greenhouse effect and how different human actions contribute to it.

Given Data / Assumptions:

• The question refers to the greenhouse effect and its causes.
• Options list deforestation, burning of fossil fuels, increase in population, and a combined option of all of the above.
• The task is to decide whether one or all of these factors significantly contribute to greenhouse gas accumulation.
• It is assumed that the basic role of greenhouse gases is understood.

Concept / Approach:
Deforestation reduces the number of trees that can absorb carbon dioxide, a major greenhouse gas, so more carbon dioxide remains in the atmosphere. Burning fossil fuels such as coal, oil, and natural gas directly releases large amounts of carbon dioxide and other greenhouse gases into the air. An increasing population accelerates demand for energy, land, and resources, indirectly leading to more deforestation and more fossil fuel use. Thus, each listed factor plays a role in intensifying the greenhouse effect, and together they contribute even more strongly.

Step-by-Step Solution:
Step 1: Consider deforestation. Fewer trees mean less carbon dioxide is absorbed, so atmospheric levels rise, strengthening the greenhouse effect. Step 2: Evaluate burning of fossil fuels, which is directly responsible for a large portion of greenhouse gas emissions worldwide. Step 3: Reflect on how population growth leads to higher energy consumption, transportation, industrial activity, and land clearing, all of which increase emissions. Step 4: Recognise that each of these three factors independently contributes to global warming. Step 5: Conclude that the combined option All of the above correctly summarises their joint impact.

Verification / Alternative check:
To verify, you can refer to summaries from climate science organisations, which usually list major drivers of climate change. Deforestation, fossil fuel combustion, and growing human population are consistently included as key causes. No single one fully explains the observed greenhouse gas increase; rather, they act together. This supports choosing the option that includes all three factors rather than just one of them.

Why Other Options Are Wrong:
Choosing only deforestation ignores the large and direct emissions from vehicles, power plants, and industry. Selecting only burning of fossil fuels overlooks how population growth amplifies the scale of such activities and how land use changes remove natural carbon sinks. Picking only increase in population without acknowledging specific emissions activities is also incomplete. Therefore, any single factor alone does not fully answer the question.

Common Pitfalls:
A common error is to focus solely on fossil fuel burning because it is often highlighted in media coverage, forgetting the reinforcing role of deforestation and population growth. Another pitfall is to underestimate indirect effects, such as how more people require more land, leading to forest loss. Remembering that climate change is a complex phenomenon driven by multiple interlinked human actions helps learners select the combined option confidently.

Final Answer:
The greenhouse effect is intensified by All of the above, that is, deforestation, burning of fossil fuels, and increase in population.