Answer:
9, 18, 27, 36, ... is an arithmetic sequence.
Last option is correct.
Explanation:
In Arithmetic sequence the difference of two consecutive terms is equal and we called this difference as common difference.
Therefore, we check in which the difference of two consecutive terms is equal.
For 1st sequence
6, 12, 15, 21, ...
12-6 = 6
15-12 = 3
The difference is not equal. Hence, it is not an arithmetic sequence.
For 2nd sequence
7, 14, 21, 36, ...
21-14=7
36-21=15
The difference is not equal. Hence, it is not an arithmetic sequence.
For 3rd sequence
8, 16, 32, 64,.....
16-8=8
32-16=16
The difference is not equal. Hence, it is not an arithmetic sequence.
For 4th sequence
9, 18, 27, 36, ...
18-9=9
27-18=9
The difference is equal. Hence, it is an arithmetic sequence.
Therefore, 9, 18, 27, 36, ... is an arithmetic sequence.
Last option is correct.