Part3(Para.14-22)the factors that cause the concentration of COz and some suggestions to deal with the problems. Step Three Detailed study Explain the important and difficult points in the text,including the usage of new words and phrases,structure of complex sentences and relevant grammar. 1.It is not very poisonous and it is present in the atmosphere in so small a quantity-only 0.034 percent-that it does us no harm. (I)poisonous:.ad.containing or having the effect of poison有毒的 e,Can you tell the difference between poisonous mushrooms and edible(可食用的) varieties? This medicine is poisonous if taken in large quantities. (2)do(sb.)harm/good:do harm/good to sb./sth.对.有害/有益 e.g.Smoking does harm to our health. (3)so+a.+a/an+n.+that如此..以至于 (3)Translate the sentence into Chinese. 它毒性不大，在大气层中的含量极小一一只占0.034%一一不会对我们造成任何 伤害。 2.What's more,that small quantity of carbon dioxide in the air is essential to life. essential n.a basic thing that you cannot live without必需品 e.g.Because I live in a remote village,I regard my car as an essential. We only had time to pack a fewessentials ad.necessary;needed必不可少的 e.g.It is essential for/to us to try to decide whether television is a blessing or a curse. Her most essential quality is kindness. 3.Plants absorb carbon dioxide and convert it into their own tissue,which serve as the basic food supply for all of animal life(including human beings, of course).In the process they liberate oxygen,which is also necessary forPart3 (Para.14-22) the factors that cause the concentration of CO2 and some suggestions to deal with the problems. Step Three Detailed study Explain the important and difficult points in the text, including the usage of new words and phrases, structure of complex sentences and relevant grammar. 1. It is not very poisonous and it is present in the atmosphere in so small a quantity — only 0.034 percent — that it does us no harm. (1) poisonous: adj. containing or having the effect of poison 有毒的 e.g. Can you tell the difference between poisonous mushrooms and edible (可食用的) varieties? This medicine is poisonous if taken in large quantities. (2) do (sb.) harm/good; do harm / good to sb./sth. 对…有害/有益 e.g. Smoking does harm to our health. (3) so + a.+ a/an +n. + that 如此…以至于 (3) Translate the sentence into Chinese. 它毒性不大，在大气层中的含量极小——只占 0.034％——不会对我们造成任何 伤害。 2. What’s more, that small quantity of carbon dioxide in the air is essential to life. essential n. a basic thing that you cannot live without 必需品 e.g. Because I live in a remote village, I regard my car as an essential. We only had time to pack a few essentials. adj. necessary; needed 必不可少的 e.g. It is essential for/to us to try to decide whether television is a blessing or a curse. Her most essential quality is kindness. 3. Plants absorb carbon dioxide and convert it into their own tissue, which serve as the basic food supply for all of animal life (including human beings, of course). In the process they liberate oxygen, which is also necessary for