Elk now live almost solely in the Rocky Mountains, which would make it seem that elk are mountain dwellers, while they once ranged over virtually all of the continental United States except for a small strip in the extreme Southwest.

1. Elk now live almost solely in the Rocky Mountains, which would make it seem that elk are mountain dwellers, while
2. The fact that elk now live almost solely in the Rocky Mountains would make it seem that they are mountain dwellers, but
3. It would seem that elk would be mountain dwellers because of their living now solely almost in the Rocky Mountains, but still
4. Now living almost solely in the Rocky Mountains, it would seem that elk were mountain dwellers, although
5. It seems that elk would be mountain dwellers from the fact that they now live solely almost in the Rocky Mountains, since

The answer is A. But it seems to conflict with the rule that which can not refer to a sentence before.