Answer:
Option (B)
Step-by-step explanation:
Given sequence is 45, 135, 405, 1215, 3645..........
Since it's a geometric sequence,
Common ratio of each successive term to the previous term
r = 
First term of the sequence 'a' = 45
Explicit formula of a geometric sequence will be,


Recursive formula of this sequence will be,
, 
Therefore, Option (B) will be the answer.