Answer:
D
Explanation:
an = 3/4 × an-1
let's see for n = 2
a2 = 3/4 × a1 = 3/4 × 4
n = 3
a3 = 3/4 × a2 = 3/4 × 3/4 × a1 = 3/4 × 3/4 × 4 = 9/16 × 4
so, we see, we multiply 3/4 one time less than n by itself and then by 4.
that makes D the correct answer.
the multiplication by (n - 1) in answer C would add 3/4 n-1 times instead of multiplying it n-1 times.
to apply n-1 multiplications we need to use n-1 as exponent.