In ΔABC shown below, Line segment AB is congruent to Line segment BC:

Triangle ABC, where sides AB and CB are congruent

Given: line segment AB≅line segment BC

Prove: The base angles of an isosceles triangle are congruent.

The two-column proof with missing statement proves the base angles of an isosceles triangle are congruent:

Statement Reason
1. segment BD is an angle bisector of ∠ABC. 1. by Construction
2. ∠ABD ≅ ∠CBD 2. Definition of an Angle Bisector
3. 3. Reflexive Property
4. ΔABD ≅ ΔCBD 4. Side-Angle-Side (SAS) Postulate
5. ∠BAC ≅ ∠BCA 5. CPCTC

Which statement can be used to fill in the numbered blank space?
line segment BD ≅ line segment AC
line segment BD ≅ line segment BD
line segment AC ≅ line segment AC
line segment AD ≅ line segment DC