The children _____ for the accident. After all, they were so young. [ ]

A. should not be to blame

B. not to be blamed

C. were not to blame

D. were to not blame

设条件 p：2x²-3x+1≤0，条件q：x²-（2a+1）x+a（a+1）≤0，若￢p是￢q的必要不充分条件，求实数a的取值范围．