I would say d. There are many strengths.
I say this because limitations tie in to the opposing side of the idea being the strengths of it.
I think it is they have wing I could be wrong
If you can type the answer then Henry could give Ribsy a bow to look better during the dog show.
It really depends on what type of swallow but 3 1/2 to 4 1/2 inches.
Have attached the picture, hope that helps...