Answer: A, B, C
A para methoxy group donates by +M directly to the charged ring positions, whereas at the meta position only its -I effect operates, so 4-OMe > 3-OMe and 4-OMe > benzyl. A nitro group destabilises the cation. At the para position the nitro group sits on a carbon that bears positive charge in a resonance structure (-M and -I), so 4-nitro is worse than 3-nitro (only -I) and worse than benzyl.