Is the answer choice I selected right?!

The Y coordinates of #A'#, #B'# and #C'# are numbers opposite to the respective coordinates in #A#, #B#, and #C#, so the triangle #A'B'C'# can be made from #ABC# by reflection over #X# axis.

Further, two triangles #ABC# an #A'B'Ç'#, the one when reflected over #x#-axis are always congruent as corresponding sides are equal and hence Answer D is wrong.

Let a corner (vertices) on a triangle be #P#
Let one triangle be #"a and the other triangle "b#

Given that there is a reflection about the x-axis and congruency exists;

then if #P_a->(x_a,y_a)# then the corresponding point on the other triangle #P_b->(x_b,y_b)=(x_a,-y_a)#

In other words the value of #x# for corresponding vertices (corners) will be the same. However, the #y# value in one will be #(-1)xxy# of the other.

So if one corner is #(-1,7)# then the other will be #(-1,-7)#

So we have #(x,y)->(x,-y)#

The #-># means 'maps to' or put another way; they are related in some way and there is some form of 'function' that links them.

Very loosely speaking, function is a mathematical term that can be interpreted as 'formula'