The whole text consists of 25 paragraphs. The following sentences are the main ideas of each paragraph. Please match each of the following main ideas with the appropriate paragraph number of the text. ______ The experiment was implemented in the normal classroom teaching with the cooperation of teachers and students. ______ Students are asked to list and explain more factors which have an impact on global warming and greenhouse effect. ______ Students learn global warming phenomenon and the Earth energy balance through viewing short video clips in the first two activities. ______ Students conduct experiments to learn about greenhouse gases, reduce their greenhouse gas emissions and recalculate their ecological footprint in the rest activities. ______ Students' knowledge about the greenhouse effect and global warming is tested in three questions.