Answer:
D.
.
Step-by-step explanation:
Given
In triangle ABC a line segment AB is congruent to line segment BC.
Given: 
To prove that the base angles of an isosceles triangle are congruent.
i.e 
1.Statement: Segment BD is an angle bisector of 
Reason: By construction.
2.Statement: 
Reason: By definition of an angle bisector.
3.Statement: 
Reason: Reflexive property .
4. Statement: 
Reason: Side-Angle-Side(SAS)
Postulate
5.Statement:
Reason: CPCT.
Hence proved.