Answer: D) 9, 15, 21, 27, ...
Explanation:
Notice that the difference (d) for each option is 6.
Divide 2019 by 6 to see what the REMAINDER is (this is the first term).
2019 ÷ 6 = 336 r.3
None of the options start with 3 so the next option would be 3 + 6 = 9.
The only option that starts with 9 is option D.