Noah is baking a two-layer cake, in which the bottom layer is a circle and the top layer is a triangle. If segment AB = 5 inches and arc AB≅ arc AC, what does Noah know about the top layer of his cake?

Circumscribed circle D around triangle ABC, arcs AB and AC are congruent.

segment AB is twice the length of segment BC because their arcs are congruent; therefore, ΔABC is an isosceles triangle.
segment AB is twice the length of segment BC because their arcs are congruent; therefore, ΔABC is an equilateral triangle.
segment AB ≅ segment BC because their arcs are congruent; therefore, ΔABC is an isosceles triangle.
segment AB ≅ segment BC because their arcs are congruent; therefore, ΔABC is an equilateral triangle.