B. I hope this help please let me know if it's correct.
Answer:
SAS theorem
Step-by-step explanation:
If
and m∠ECD = m∠BCA, then the triangles are similar by the SAS theorem.

So,
and m∠ECD = m∠BCA because vertical angles are congruent
Therefore ΔECD is similar to ΔBCA by SAS theorem
You could do three tenths