Answer:  The correct option is
(b) Square the number of the term, n.
Step-by-step explanation:  We are given to examine the following sequence :
 1,   4,   9,   16,  25,   .   .   . 
Also, we are to state the reason behind 36 being the next term in the sequence.
We see the following pattern in the terms of the given sequence :

Following the above pattern, we arrive at the n-th term of the sequence as follows :

Since we are to find the next, .i.e., the sixth term of the sequence, so 
if n = 6, then

Thus, to get the n-th term, we square the number of the term.
The correct option is
(b) Square the number of the term, n.