Answer:
Option D.
Explanation:
Given: See the diagram.
Prove: DC = DB
Perpendicular bisector theorem : If a point lies on the perpendicular bisector of a segment, then it is equidistant from the segment's endpoints.
Proof:
Statement 1:

Reason: Given.
Statement 2: AG=GC
Reason: Given
Statement 3:
is perpendicular bisector of
.
Reason: Deduced from steps 1 and 2
Statement 4: DA=DC
Reason: Perpendicular bisector theorem
Statement 5:

Reason: Given
Statement 6:AH=HB
Reason:Given
Statement 7:
is perpendicular bisector of
.
Reason: By definition of perpendicular bisector.
Statement 8: DA=DB
Reason : Perpendicular bisector theorem
Statement 9: DC=DB
Reason: Transitive property of equality.
Hence proved.
Therefore, the correct option is D.