Sentence: The best friend ... I have ever had.

Jack is the best friend ___ I have ever had. (A) which (B) who © that (D) with who
The answer is option C. Is option B also acceptable?

Hi Sitifan…
It seems that your sentence is already complete without inserting any word from your suggestion (A), (B) & ©.
I would like to know [color=blue]if I am correct from any of the communicators…
Thanks…

Sitifan, we normally wouldn’t put anything in that slot.