Final answer:
The correct answer is C. present perfect progressive.
Step-by-step explanation:
The correct answer to this question is C. present perfect progressive. The present perfect progressive tense is used to talk about an action that started in the past, continues in the present, and may continue into the future.
In this case, the speaker is referring to a period of time starting in the past (12 years ago) and continuing up until next month. Example: 'My best friend and I have been knowing each other for 12 years.'