X+4=16 1&2 step equation

In the figure below, segment ac is congruent to segment ab: which statement is used to prove that angle abd is congruent to angle acd? a.)triangle acd is similar to triangle abd. b.)triangle acd is congruent to triangle abd. c.)segment a.d. is congruent to segment ac. d.)segment a.d. is congruent to segment dc.