APMOPS 2001 Question 4

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, ...