presents a fully developed position in answer to the question with relevant, fully extended and well supported ideas
如果你问，什么叫fully extended / well supported?就是丰满的主体段。
is well organized and well developed, using clearly appropriate explanations, exemplifications, and/or details
一般来说，想要雅思作文写的好，至少需要含有两个主体段，且每个主体段都必须拥有明确的主题句即topic sentence，并有若干句supporting sentences，也就是我们常说的论据与论点。建议大家在练习议论文写作时遵循几个简单的原则，就能够迅速完成理由段，并且构建连贯和理由充分的议论文哦!
Write a topic sentence for each paragraph you plan to write. Each topic sentence should relate to your thesis statement and introduce what the paragraph will be about. If you find that the topics you want to discuss do not support the thesis statement you have written, revise your thesis statement or reconsider your topic sentences.
Write ideas that support your topic sentences. The topic sentence for each paragraph tells the reader what the paragraph will be about. The ideas stated in the rest of the paragraph should all relate to the topic sentence.
Hobbies are important for many reasons. First, a hobby can be educational. For example, if the hobby is stamp collecting, the person can learn about the countries of the world and even some of their history. Second, engaging in a hobby can lead to meeting other people with the same interests. A person can also meet other people by going to the school. Third, a person's free time is being used in a positive way. The person has no time to be bored or get into mischief while engaged in the hobby. Finally, some hobbies can lead to a future job. A person who enjoys a hobby-related job is more satisfied with life.
后面紧跟的First，second, third都是为了支持前面的第一句话。此外，在每一个点，又加入新的支持。比如在First句后面，又加了For example，来支持前面的观点，这样层层递进，文章就看起来格外的脉络清晰。这句中，很明显主题句就是Hobbies are important for many reasons.
但本段也并非完美无瑕哦~ A person can also meet other people by going the school"与hobby重要的原因没有关系，因此削弱了整个段落的连贯性与统一性，应该被去掉。