The twins resemble each other very much. I can't tell which is which

The twins resemble each other very much. I can't tell which is which
A. The twins resemble each other so much that I can't tell which is which
B. Even though the twins resemble each other very much, I can't tell which is which
C. So long as the twins resemble each other very much, I can't tell which is which
D. Unless the twins resemble each other very much, I can't tell which is which