Answer: I believe the answer is stroke
Explanation:
it would be (D) because you cant see an atom without a microscope and a model is a larger model of the actual thing.
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.
I believe the answer might be A