Answer: The correct option is (C)

Step-by-step explanation: We are given to find the common ratio for the following geometric sequence :
64, 16, 4, 1, . . .
We know that
if a(n) represents the n-th term of a geometric series, then the common ratio is given by

For the given geometric sequence, we have
a(1) = 64, a(2) = 16, a(3) = 4, a(4) = 1, . . .
So, the common ratio r will be given by

We have

Thus, the required common ratio for the given geometric sequence is

Option (C) is CORRECT.