Explanation:
The Blue Ridge Mountains are a physiographic province of the larger Appalachian Mountains range. The mountain range is located in the eastern United States, and extends 550 miles southwest from southern Pennsylvania through Maryland, West Virginia, Virginia, North Carolina, South Carolina, Tennessee, and Georgia.[1] This province consists of northern and southern physiographic regions, which divide near the Roanoke River gap.[2] To the west of the Blue Ridge, between it and the bulk of the Appalachians, lies the Great Appalachian Valley, bordered on the west by the Ridge and Valley province of the Appalachian range.
<span> In the given context, the meaning of the word 'disorder' is : an abnormal condition. The main feature of the prefix dis- is that in makes word to function in an opposite meaning. Since the sentence is about the nervous system, the only logically and contextually correct option is the last one, as it represents negative meaning opposing to the needed condition. It is not a procedure, not an organ and there is no context clues that point out on it as illness. Also, disorder of nervous system is a stable biological term.
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