we know that
The distance 's formula between two points is equal to

Step 
<u>Find the distance MN</u>

Substitute in the distance's formula



Step 
<u>Find the distance NL</u>

Substitute in the distance's formula



Step 
<u>Find the distance LM</u>

Substitute in the distance's formula



Step 
<u>Find the perimeter of the triangle LMN</u>
we know that
The perimeter of a triangle is equal to the sum of the three length sides
In this problem

substitute the values in the formula


therefore
<u>the answer is the option D</u>
the perimeter of the triangle LMN is equal to 