Answer:
A
Explanation:
To find the nth term of a sequence :
We find the jump between each terms :
21 to 17 is -4
17 to 13 is -4
13 to 9 is -4
There -4 will go before the n
Then we find the 0th term :
Opposite of -4 is +4
21 + 4 = 25
Our final answer is -4n + 25
Option A
Hope this helped and have a good day