Answer:
The additional information that needed is m∠ABD = m∠CDB ⇒ C
Explanation:
In the given figure
Triangles ADB and CBD are congruent by ASA under these conditions
- m∠ADB = m∠CBD
- DB = BD ⇒ the side joining the congruent angles
- m∠ABD = m∠CDB
Let us see the given to find the correct answer
∵ ∠ADB and ∠CBD have the same mark
∴ m∠ADB = m∠CBD ⇒ (1) given
∵ Side DB is a common side in the two triangles
∴ DB = BD ⇒ (2) given
∵ ∠ABD and ∠CDB are the angles at the end of BD
∴ m∠ABD must equal m∠CDB ⇒ (3) to prove the congruency using ASA
∴ The additional information that needed is m∠ABD = m∠CDB