Answer:
Hello!
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1. Because fragments make it hard to understand your sentence<u>.</u>
2. Proofreading your writing can be very interesting. <u>You</u> can find out what you have written.
3. While procrastinating and worrying, the exam<u> will get </u>closer and closer.
5. The students <u>must</u> have a good understanding of grammar.
6. Anyone who <u>hasn't</u> done their grammar assignment must have had something better to do.
7. Studying can be exciting, rewarding and sometimes really <u>annoying</u>.
8. The only excuse <u>there</u> was, that <u>their</u> exam started early.
9. When you use an apostrophe, make sure you know its proper use. Its often used incorrectly.
10. The student didn't get<u> any</u> marks for the assignment.
Hope this helped you!
Explanation: For question 4 and 9 i couldn't find any errors.