Explanation:

1. Understanding the question:
The question is asking about the time of the sunset tomorrow. To answer this question, we need to use future tense.

2. Using the correct structure:
In English, when asking about a future event, we use the auxiliary verb "will" followed by the base form of the main verb. In this case, we need to use "will" followed by "the sun set."

3. Formulating the answer:
To answer the question correctly, we need to use the future tense structure. The correct answer is "will the sun set."

4. Providing a detailed explanation:
To further explain the answer, we can break it down into the following points:

- The question is asking about the time of the sunset tomorrow.
- In English, when talking about future events, we use the auxiliary verb "will" followed by the base form of the main verb.
- In this case, the main verb is "set." So, we need to use "will" followed by "the sun set" to form the correct sentence.
- The word "will" indicates a future action, and "the sun set" is the base form of the verb that describes the action of the sun going below the horizon.
- By using "will the sun set," we are correctly asking about the time when the sun will go below the horizon tomorrow.

5. Final answer:
The correct answer to the question "What time ---- (the sun/set) tomorrow?" is "will the sun set."