1. One of the reasons for underperforming is that you're not taking good enough notes.

$-$ Dẫn chứng ở câu thứ nhất.

2. Problems of Hurriedly scawled notes is difficult to make sense of when I come to revise from them, or even to write an essay based on them.

$-$ Dẫn chứng ở câu thứ hai.

3. It's failing to get a strong enough grasp of the topic.

$-$ Dẫn chứng ở vế sau của câu thứ ba.

4. Because they are readable, useful and logically organized.

$-$ Dẫn chứng ở câu thứ tư.

5. I should try to write them up at the end of the day, while they're still fresh in my mind.

$-$ Dẫn chứng ở vế sau của câu kết đoạn.

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$@haanx2$

`1.` It is that you're not taking good enough now. 

`-` Dẫn chứng: One of the reasons you may have identified for underperforming is that you're not taking good enough notes.

`2.` Problems of Hurriedly scrawled notes are difficult to make sense of when I come to revise from them, or even to write an essay based on them.

`-` Dẫn chứng: Hurriedly scrawled notes from class can be difficult to make sense of when you come to revise from them, or even to write an essay based on them. 

`3.` It's failing to get a strong enough grasp of the topic.

`-` Dẫn chứng: It's all too easy to misunderstand your own notes and fail to get a strong enough grasp of the topic.

`4.` Because they are readable, useful, and logically organized.

`-` Dẫn chứng: It's imperative, therefore, that you produce good notes from each of your classes and from the book you use - notes that you can read, that are useful, and that are logically organised.

`5.` I should try to write them up at the end of the day, while they're still fresh in my mind. 

`-` Dẫn chứng: If you make notes by hand- in class, for example - try to type them up at the end of the day, while they're still fresh in your mind.