The statement The greenhouse effect is caused solely by human activity should be considered:

Introduction / Context:
This environmental science question asks you to evaluate a statement about the greenhouse effect and human influence on climate. Climate change discussions often mix natural processes and human impacts, so it is important to separate what is naturally occurring from what humans have added or intensified.

Given Data / Assumptions:

• The statement claims that the greenhouse effect is caused solely by human activity.
• Options invite you to decide whether this statement is correct or incorrect and to justify your choice.
• Basic knowledge of greenhouse gases and climate processes is assumed.

Concept / Approach:
The greenhouse effect is a natural process in which certain gases in the atmosphere, such as water vapour, carbon dioxide, methane, and nitrous oxide, trap heat radiated from Earth surface and keep the planet warmer than it would be without them. Without this natural greenhouse effect, the average surface temperature would be far below freezing, making life as we know it impossible. Human activities, such as burning fossil fuels, deforestation, and industrial agriculture, increase the concentrations of greenhouse gases, particularly carbon dioxide and methane. This enhanced greenhouse effect leads to global warming and climate change. Therefore, the basic greenhouse effect is natural, while the recent rapid increase in its strength is largely due to human actions.

Step-by-Step Solution:

Verification / Alternative check:
Climate science texts and reports from scientific organisations explain that the greenhouse effect has been operating for billions of years. They distinguish the natural greenhouse effect, which keeps the climate suitable for life, from the enhanced greenhouse effect caused by anthropogenic emissions. Graphs of atmospheric carbon dioxide over geological time also show natural variations before human society emerged. This body of evidence confirms that the underlying greenhouse effect is natural, and that human activity is responsible for intensifying it, not for creating it from nothing.

Why Other Options Are Wrong:

Correct, because greenhouse gases are produced only by factories and vehicles is wrong because greenhouse gases also come from volcanoes, wetlands, oceans, decomposition, and many natural sources.

Incorrect, because there is no such thing as a greenhouse effect is incorrect because the greenhouse effect is a well established physical process backed by observations and measurements.

Correct, because natural sources of greenhouse gases do not exist is wrong because it denies the large role of natural processes such as respiration, volcanic emissions, and water vapour evaporation in the atmosphere.

Common Pitfalls:
A common misunderstanding is to confuse the greenhouse effect with recent human caused global warming and to claim that the entire effect must be human made. Another pitfall is the opposite extreme, where some people say that everything is natural and human actions do not matter, which ignores the rapid rise in greenhouse gas levels since industrialisation. For exam purposes, remember this balanced view: the greenhouse effect is a natural and necessary process, but human activities have strengthened it, leading to climate change concerns.

Final Answer:
The statement is Incorrect, because the greenhouse effect is a natural process that is strengthened by human activities rather than being caused solely by them.