"Twice the previous term" means the previous term is multiplied by 2 to get the present term. In other words, the next term is 2 times the present term.
The first term is 9 (given).
The second term is 2×9 = 18.
The third term is 2×18 = 36.
You can figure the 4th term, but there is no need. This is sufficient to identify the correct answer as ...
... D. 9, 18, 36, 72