12/20 is the answer I think. I hope this helps you!!
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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.
B double helix and linked with hydrogen bonds
The nucleic acid is DNA and would be found in the cell’s nucleus.
In short, Your Answer would be Option D
Hope this helps!