The range of a set of data is the difference between the highest and lowest values in the set.
And to find the range, first order the data from least to greatest. Then subtract the smallest value from the largest value in the set.
An area with unifying characteristic is called as a region. The region is a broad geographic area, which is differentiated from other because of the similar features. In a region one or more than one types vegetational climax might be present. It is the continuous and extensive part of the surface. The area in a region is indefinite.
Hence, the given blank can be filled with region.
The answer to your question would have to be C