Which side has an equal measure to bc?

a. de
b. ab
c. ef
d. df

In the given diagram, we are given two triangles, triangle ABC and triangle DEF.

And we are given a line or reflection l.

Triangle DEF is the mirror image of triangle ABC.

Therefore, all sides of the triangle ABC would be congruent to sides of triangle DEF.

AB = DF

AC = DE and

BC = EF.

We can see than BC is the smallest side of triangle ABC and EF is the smallest side of triangle DEF.

its the fourth option