Well yes it matters, we are not talking about identical white and black balls
Now the solution
We know that the total number of kids = 6
Since boys can stand in the corners, we need to know specifically how many boys and girls are there.
If number of girls is 4 then number of boys = 2
This is sufficient to calculate the number of arrangements.
(Not required but I will go ahead and get the number of arrangements)
First we fill in the corners with 2 girls, can be done in 4*3 ways
Now we can arrange the remaining 4 kids in any order = !4
Total number of arrangements = 4*3*!4
there are 12 different ways to fill first and last spot
Let number of girls be n then number of ways to fill the corners= n*(n-1)
n=-3 or n=4
4 is the only possible value, we can solve as above to get the arrangements.
Answer is D.