[AMEDIO]

Following compound A spontaneously changes into
http://img846.imageshack.us/i/51646289.png/
ONE OR MORE THAN ONE OPTIONS MAY BE CORRECT.

[Honclbrif]

If you're trying to get us to do your homework, at least give us your best guess and pretend like you're trying to better understand the problem...

[MethylNeptuneAcetate]

well, only B and A have the right structure between the nitrogen and the ring, and it makes the most sense that the lone pair on the nitrogen would attack the far side of the double bond in conjugation with the carbonyl (resonance makes this position more electrophilic. I can draw the structures if you want.), which leads to answer B. Also, if the nitrogen attacked the carbonyl, it wouldn't end up bonded to the oxygen, but to the carbon the oxygen is bonded to.

Also doing so forms a favorable six membered ring.

[ultima]

Mechanism should follow something like this. I agree with compound B being the only correct connectivity. But, if the nitrogen did attack directly at the carbonyl, you would not end up with a 6 member ring, I think i count an 8 member ring, which you have not shown as an answer (and would be fairly unfavourable anyway).

Generally shown by
1,4-michael addition (nitrogen attacking end of double bond).
Proton transter (to make enol)
Equilibration (to make ketone, which i believe is the more favoured/stabled state).



So, in all, I believe B is the only correct answer.