According to Hückel's rule

Correct option is B

​Aromatic compounds

Aromatic compounds or arenes are organic compounds "with a chemistry typified by benzene" and "cyclically conjugated."Aromatic compounds are now defined as cyclic compounds satisfying Hückel's Rule. 

In organic chemistry, Hückel's rule predicts that a planar ring molecule will have aromatic properties if it has 4n + 2 π-electrons, where n is a non-negative integer. A cyclic ring molecule follows Hückel's rule when the number of its π-electrons equals 4n + 2, although clear cut examples are really only established for values of n = 0 up to about n = 6.

Criteria for simple aromatics are:

1. the molecule must have 4n + 2 (a so-called "Hückel number") π electrons (2, 6, 10, ...) in a conjugated system of p orbitals (usually on sp²-hybridized atoms, but sometimes sp-hybridized);
2. the molecule must be (close to) planar (p orbitals must be roughly parallel and able to interact, implicit in the requirement for conjugation);
3. the molecule must be cyclic (as opposed to linear);
4. the molecule must have a continuous ring of p atomic orbitals (there cannot be any sp³ atoms in the ring, nor do exocyclic p orbitals count).

Antiaromatic compounds

Antiaromaticity is a chemical property of a cyclic molecule with a π electron system that has higher energy, i.e., it is less stable due to the presence of 4n delocalised (π or lone pair) electrons in it, as opposed to aromaticity. Unlike aromatic compounds, which follow Hückel's rule ([4n+2]π electrons) and are highly stable, antiaromatic compounds are highly unstable and highly reactive. 

The term 'antiaromaticity' was first proposed as "a situation in which a cyclic delocalization of electrons is destabilising". The IUPAC criteria for antiaromaticity are as follows:

1. The molecule must be cyclic.
2. The molecule must be planar.
3. The molecule must have a complete conjugated π-electron system within the ring.
4. The molecule must have 4n π-electrons where n is any integer within the conjugated π-system.

This differs from aromaticity only in the fourth criterion: aromatic molecules have 4n +2 π-electrons in the conjugated π system and therefore follow Hückel’s rule. Non-aromatic molecules are either noncyclic, nonplanar, or do not have a complete conjugated π system within the ring.

M has 10 pi electrons (including lone pair on nitrogen atom)

N has 6 pi electrons. Boron atom is sp² hybridized.