Answer:
Option (4).
Explanation:
Given question is incomplete; here is the complete question.
Jefferson is plotting the vertices of an isosceles right triangle on a coordinate graph. He has plotted the two points shown. Where should he plot the third point? 
The point is on the graph is (-2,-4) (4,-4) 
 The options are
 (-2,-9) 
(3,1) 
(-2,0) 
(4,2) 
 Distance between (-2, -4) and (4, -4) = 6 units
Now we will check every option,
1). For point (-2, -9),
Distance between (-2, -4) and (-2, -9) = 

Similarly, distance between (4, -4) and (-2, -9) = 

None side is equal. So it's not an isosceles triangle.
2). For a point (3, 1),
Distance between (3, 1) and (-2, -4) = 

Distance between (3, 1) and (4, -4) = 

Since none side of the triangle are not equal, triangle is not an isosceles triangle.
3). For (-2,0),
Distance between (-2, 0) and (-2, -4) = 4
Distance between (-2, 0) and (4, -4) = 
 =
 = 

None side is equal so the triangle formed is not an isosceles triangle.
4). For a point (4, 2),
Distance between (4, 2) and (-2, -4) = 

Distance between (4, 2) and (4, -4) = 

We find the two sides of this triangle measure 6 units therefore, its an isosceles triangle.
Option (4) will be the third point.