The electronegativity of the following elements
increase in the order

We know that Electronegativity increases as we move left to right in a period and decreases as we go down a group. 

Now,Nitrogen has higher electronegativity than Carbon 

And Phosphorus has higher electronegativity than Silicon.

Therefore, the electronegativity of the following elements increase in the order $\mathrm{Si},\mathrm{P},\mathrm{C},\mathrm{N}$,

Hence, option(C) is the answer.