In the periodic table.... in periods- from left to right electro negativity of the atom increases.... so the correct answer for your question is option -A

Electronegativity is the ability of an atom to attract electrons towards itself in a chemical bond. It is a property that increases across a period from left to right and decreases down a group in the periodic table.

The given elements are Si (Silicon), P (Phosphorus), C (Carbon), and N (Nitrogen). We need to compare their electronegativity and determine the order in which it increases.

Electronegativity trend across a period:
- Electronegativity generally increases across a period from left to right. This is because the effective nuclear charge, which is the positive charge experienced by the valence electrons, increases as we move from left to right across a period. The increased nuclear charge pulls the valence electrons closer to the nucleus, making it easier for the atom to attract electrons.

Comparison of the given elements:
- Silicon (Si) is located to the left of Phosphorus (P) in the periodic table and has a lower electronegativity. This is because Si has a lower effective nuclear charge compared to P, which makes it less capable of attracting electrons.
- Carbon (C) is located to the left of Nitrogen (N) and has a lower electronegativity. Similarly, C has a lower effective nuclear charge compared to N, making it less electronegative.

Order of increasing electronegativity:
Based on the above comparisons, we can conclude that the electronegativity of the given elements increases in the order of:

a) Si, P, C, N

Explanation:
- Silicon (Si) has the lowest electronegativity among the given elements.
- Phosphorus (P) has a higher electronegativity than Si.
- Carbon (C) has a higher electronegativity than both Si and P.
- Nitrogen (N) has the highest electronegativity among the given elements.

Therefore, the correct answer is option 'A': Si, P, C, N.