How do you figure it out?

ya try B

Step-by-step explanation:

m∠BEC + m∠CED = m∠BED; Angle Addition Postulate

Step-by-step explanation:

For example : If ∠MON and ∠NOK are joined such that NO is the common line segment between then then the new angle will be ∠MOK or ∠KOM.

In given figure , m∠BEC and m∠CED are joined and they have common line segment CE , then the new angle m∠BED= m∠BEC + m∠CED

Hence, the correct statement that completes the given proof :

m∠BEC + m∠CED = m∠BED; Angle Addition Postulate