Answer:
D
Explanation:
F(x) =

the denominator cannot be zero as this would make F(x) undefined
to find the value that x cannot be, equate the denominator to zero and solve for x and if this value of x makes the numerator non zero , then it is a vertical asymptote
4x - 4 = 0 ( add 4 to both sides )
4x = 4 ( divide both sides by 4 )
x = 1
the x = 1 is the vertical asymptote