Question

Which two triangles are similar?    

A.A and B  B.B and C  C.C and D  D.A and C  

Answer 1

the answer is C=> C&D

Answer 2

It is clear that the  triangles  C and D are right angle triangles.  One side (opposite side) is common or parallel.      Hence the other sides are also parallel to the sides in the other triangle.

hence the triangles are similar.   In fact,  triangle C is 1/4 the area of triangle D.