The correct answer would be B. 2/(x + 8)
When you are completing composite functions, you place the entire second function in for x in the first function. Since the letter f comes first in f o g. then we start with the f(x) equation.
f(x) = 2/x
Now since g comes next, we take the entire equation for g(x) and substitute it in.
f o g = 2/(x + 8)
This is answer B.