AMO 2027 Grades 6-7 SET 9 - Self-study Question 9

If numbers are arranged in 3 rows A, B and C according to the following table, which row will contain the number 1000?
A 1, 6, 7, 12, 13, 18, 19, ...
B 2, 5, 8, 11, 14, 17, 20, ...
C 3, 4, 9, 10, 15, 16, 21, ...