Students practice using interjections like "Hurray," "Ouch," and "Yippee" in sentences.

To solve the problem, we need to complete each sentence using an appropriate adverb from the given list: Slowly, Completely, Suddenly, or Quickly. Let's analyze each sentence and choose the most suitable adverb.

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Sentences and Solutions:

1. I finished my work _________.
- Adverb: Quickly
- Explanation: The context suggests that the work was completed in a short amount of time. "Quickly" fits best here.
- Completed Sentence: I finished my work quickly.

2. I didn't understand what he said _________.
- Adverb: Suddenly
- Explanation: The phrase "didn't understand" implies a sudden lack of comprehension. "Suddenly" fits well here.
- Completed Sentence: I didn't understand what he said suddenly.

3. I have been waiting for the bus _________.
- Adverb: Slowly
- Explanation: Waiting for something often involves a gradual passage of time. "Slowly" is appropriate here.
- Completed Sentence: I have been waiting for the bus slowly.

4. I applied for this job _________.
- Adverb: Completely
- Explanation: Applying for a job typically involves completing all necessary steps. "Completely" fits best here.
- Completed Sentence: I applied for this job completely.

5. I had no idea about the content.
- Adverb: Suddenly
- Explanation: Not knowing about something can happen unexpectedly. "Suddenly" works well here.
- Completed Sentence: I had no idea about the content suddenly.

6. I have got my grades.
- Adverb: Quickly
- Explanation: Receiving grades can sometimes be a quick process. "Quickly" fits here.
- Completed Sentence: I have got my grades quickly.

7. I have read the whole book.
- Adverb: Completely
- Explanation: Reading the whole book means finishing it entirely. "Completely" is the best choice.
- Completed Sentence: I have read the whole book completely.

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Final Answer:

1. I finished my work quickly.
2. I didn't understand what he said suddenly.
3. I have been waiting for the bus slowly.
4. I applied for this job completely.
5. I had no idea about the content suddenly.
6. I have got my grades quickly.
7. I have read the whole book completely.

Boxed Answer:
\[
\boxed{
\text{1. quickly, 2. suddenly, 3. slowly, 4. completely, 5. suddenly, 6. quickly, 7. completely}
}
\]