If the coefficient of x in (1+x)¹⁰¹(1 - x + x²)¹⁰⁰ is b, then which of the following is/are correct? (rEW)
A. b = 0 when n = 3r
B. b ≠ 0 when n = 3r
C. b≠ 0 when n = 3r +1
D. b = 0 when n = 3r + 2