Global warming is caused mainly by increased

  1. carbon dioxide and methane in the atmosphere
  2. rainfall
  3. oxygen in the atmosphere
  4. nitrogen in the soil
Answer

A) carbon dioxide and methane in the atmosphere

These greenhouse gases trap heat. O Level Biology · Topic 19 Relationships of Organisms with One Another and with the Environment · 19.4 Effects of humans on ecosystems

Biology MCQ · More O Level Biology: Organisms and the Environment MCQs · Practise