Task：The diagram below illustrates the carbon cycle in nature.
思路解析：
1. 需要看懂图形之间的顺序，并找到流程的起点和终点;
2. 需要理解图形之间的因果关系;
3. 需要学会描述事物之间的转换：如空气变成固体;
4. 需要理解和推测文字描述和图形步骤之间的因果关系：如前提条件，过程，后果。
雅思写作(ielts.zhan.com/)参考范文：
The flow chart shows how the cycle of carbon is formed in the nature completely. Overall, this process has 3 main parts, including carbon absorbing, transferring and releasing.
Firstly, under the exposure to sunlight, plants like green trees begin a process known as photosynthesis which absorbs CO2 from the air. After the death and decay of these plants, the organic carbon is then transferred underground. Similarly, the carbon accumulated in dead animals which feed on plants in life, such as sheep, is also deposited in soil. Being pressed and mingled in deep earth for a long term, a part of trapped carbon is converted into the form of fossil or fossil fuels.
In terms of releasing carbon back, there are generally 3 ways. Organically, physical respiration from both plants and animals produces and exhales large amount of carbon as CO2 into atmosphere. Spontaneously, root respiration of plants also extracts fixed carbon from soil. Besides, man-made activities that burn fossil fuels like car running or factory manufacturing make serious gas emissions of CO2 in air.
Finally, the entrance of CO2 into atmosphere activates this natural cycle which consists of sun, air, creatures, land and human activities.
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