Answer:
C
Step-by-step explanation:
The standard form for the explicit formula of a geometric sequence is given by:
![a_n=a\cdot(r)^{n-1}](https://tex.z-dn.net/?f=a_n%3Da%5Ccdot%28r%29%5E%7Bn-1%7D)
Where a is the initial term, r is the common ratio, and n is the nth term.
Our sequence is: 8, 4, 2, 1...
So, we can see that our initial term or a is 8.
Each subsequent term is half of the previous one. So, our common ratio is 1/2.
Let's substitute 8 for a and 1/2 for r to acquire:
![a_n=8\cdot(\frac{1}{2})^{n-1}](https://tex.z-dn.net/?f=a_n%3D8%5Ccdot%28%5Cfrac%7B1%7D%7B2%7D%29%5E%7Bn-1%7D)
So, our answer is C.
And we're done!