Answer:
I'm HAVING coffee.
Step-by-step explanation:
I'm breaks down to the words I AM. This means we could either be talking about the present or the future.
In this case we only have answers that are either in the past tense(Has) or in the present tense(Have, and Having).
We know that we are using present tense so we can eliminate the answer of has, leaving us with having, and have.
The correct grammar would be I'm having coffee, or I am having coffee. If we were to use have though, that would be incorrect grammar. I'm have coffee, or I am have coffee.
-Hope this helped