Answer:
B. The SAS Postulate
Step-by-step explanation:
In the given figure, we are shown two triangles,
and
.
Since triangle ADE is inscribed in triangle ABC, both triangles must share angle
. Furthermore, let's take a look at the two legs of each triangle, if we say that their respective bases are DE and BC.
Compare the corresponding legs of each triangle with proportions:

Since two corresponding legs/sides of triangle are in a constant proportion, the triangles must be similar from the SAS (Side-Angle-Side) Postulate.