The Correct Answer: 'Has Stopped'

Explanation:

When we say "The clock is slow", it implies that the clock is currently running but is displaying a time that is behind the actual time. However, in response to this statement, when we say "It has stopped", it means that the clock is no longer running and has come to a complete halt.

Present Continuous Tense:
- The phrase "is slow" indicates the usage of the present continuous tense.
- This tense is used to describe an action that is happening at the present moment.
- In this case, the clock is currently running but is showing a time that is slower than the actual time.

Present Perfect Tense:
- On the other hand, the response "has stopped" uses the present perfect tense.
- This tense is used to describe an action that started in the past and has a connection to the present moment.
- In this case, the clock has stopped running, which is a past action that has a relevance to the current situation.

Understanding the Correct Answer:
- When we say "The clock is slow", it means that the clock is still running but showing an incorrect time.
- However, the response "It has stopped" implies that the clock is no longer running and has come to a complete stop.
- Therefore, the correct answer is "has stopped" as it accurately describes the situation where the clock is not running anymore.

Summary:
- The phrase "The clock is slow" indicates that the clock is running but showing an incorrect time.
- The response "It has stopped" means that the clock is no longer running and has come to a halt.
- The present continuous tense is used to describe an action happening at the present moment, while the present perfect tense is used to describe an action that started in the past and has a connection to the present.
- Therefore, "has stopped" is the correct answer in this context.