Considering the elements $B, C, N, F,$ and $Si,$ the correct order of their non-metallic character is:
$(a)$ $B > C > Si > N > F$
$(b)$ $Si > C > B > N > F$
$(c)$ $F > N > C > B > Si$
$(d)$ $F > N > C > Si > B$

(C) The non-metallic character of elements increases from left to right across a period. Thus,the decreasing order of non-metallic character for $B, C, N, F$ is $F > N > C > B$.
Non-metallic character decreases down a group. Comparing $C$ and $Si$ (Group $14$),$C > Si$.
Comparing $B$ and $Si$,$B$ is more non-metallic than $Si$ because $B$ is in period $2$ and $Si$ is in period $3$.
Combining these,the correct order of non-metallic character is $F > N > C > B > Si$.