No I think ans will be (C)
M will be non recursive enumerable here.
After accepting 312929 strings it will accepting inputs, but here it accepts all. So, here is a chance of forming loop.(we can think like dfa, when dfa accepts all, it forms a self loop on last state). But when we examining loop doesnot gives 'yes' answer. So, 'yes' answer not possible. According to rice theorem it will be non trivial property. So, M will be non recursive enumerable here.