6. To draw a 3 by 3 square grid you need 8 straight lines, as shown.
How many straight lines do you need to draw a $n$ by $n$ square grid?
A $n+5$
B $3 n-1$
C $n^{2}-1$
D $4(n-1)$
E $2(n+1)$
6. E To draw a $n$ by $n$ square grid requires $(n+1)$ horizontal lines and $(n+1)$ vertical lines. So, in total, $2(n+1)$ lines are required.