Which of the following are congruent?
Two squares having the same side
Two circles of same radii
Congruent shapes will have same shape and same size.
Two squares of same side would fit one over the other exactly. So they are congruent.
Two circles of the same radius would overlap each other completely. Hence they are congruent.
Two rectangles having the same length are congruent only if their breadths are also the same. Since we do not know about their breadths, we cannot say if they are congruent or not.
Two line segments of different lengths are not congruent.