Explanation:

Present Continuous:
- The question is asking about a future action, which indicates the use of the present continuous tense.
- In this case, the action of visiting is planned for the upcoming winter.
- The present continuous tense is used for actions that are planned, or already decided upon to take place in the future.
Therefore, the correct tense for the sentence "Are they visiting you next winter?" is Present Continuous.

The correct tense of the given sentence "Are they visiting you next winter?" is Present Continuous.
Here is the detailed explanation:
1. Present Continuous:
- Present Continuous tense is used to describe actions that are happening at the moment of speaking or around the current time.
- It is formed by using the present tense of the verb "to be" (in this case "are") followed by the present participle form of the main verb (in this case "visiting").
- In the given sentence, "Are they visiting you next winter?", the use of the verb "are" (present tense of "to be") and the present participle form "visiting" indicates an action that is planned or scheduled to happen in the future, but is being talked about in the present time.
2. Past Continuous:
- Past Continuous tense is used to describe actions that were happening in the past at a specific time or over a period of time.
- It is formed by using the past tense of the verb "to be" (in this case "were") followed by the present participle form of the main verb.
- The given sentence does not indicate any past action, so Past Continuous tense is not applicable.
3. Present Perfect:
- Present Perfect tense is used to describe actions that started in the past and have a connection to the present.
- It is formed by using the present tense of the auxiliary verb "have" (in this case "have") followed by the past participle form of the main verb.
- The given sentence does not indicate any past action that has a connection to the present, so Present Perfect tense is not applicable.
4. Past Perfect:
- Past Perfect tense is used to describe actions that happened before a certain point in the past.
- It is formed by using the past tense of the auxiliary verb "have" (in this case "had") followed by the past participle form of the main verb.
- The given sentence does not indicate any past action before a certain point in the past, so Past Perfect tense is not applicable.
Therefore, the correct tense for the given sentence is Present Continuous (option A).