Doctors in rural areas lack adequate transportation to such a significant degree as to make it difficult to distribute them throughout a countryside becoming increasingly populated with people fleeing the urban lifestyle.

A. lack adequate transportation to such a significant degree as to make it difficult to distribute them throughout a countryside becoming
B. lack adequate transportation to a significant enough degree as to make it difficult to distribute themselves throughout a countryside that becomes
C. lack of adequate transportation is so large as to be difficult to distribute them throughout a countryside that becomes
D. are lacking so much in adequate transportation as to be difficult to distribute throughout a countryside becoming
E. are so lacking in adequate transportation that they find it difficult to distribute themselves throughout a countryside becoming

[spoiler]Source : Grockit, OA- after some discussion/post[/spoiler]