Answer:
3
Step-by-step explanation: From one point, go over to the top/bottom of the other point then go down/up to the point (go from one point to the other) then the rise you did (1) over the run across (3) then the formula is rise over run. then divide.
Given:
The geometric sequence is:

1 -4
2 20
3 -100
To find:
The explicit formula and list any restrictions to the domain.
Solution:
The explicit formula of a geometric sequence is:
...(i)
Where, a is the first term, r is the common ratio and
.
In the given sequence the first term is -4 and the second term is 20, so the common ratio is:



Putting
in (i), we get
where 
Therefore, the correct option is B.
For a better understanding of the answer given here, please go through the diagram in the attached file.
The diagram assumes that the base of the hexagonal pyramid is an exact fit (has same dimensions as the face of the hexagonal prism).
As can be seen from the diagram, the common vertices are A,B,C,D,E,F which are 6 in number.
The bottom vertices are G,H,I,J,K,L, which, again are 6 in number.
The Apex of the pyramid, P is one more vertex.
Thus, the total number of vertices in a Hexagonal pyramid is located on top of a hexagonal prism will be the sum of all these vertices and thus will be:
6+6+1=13