Hello there!
The answer to this question will be answer choice A.
When using the SAS postulate, we need two pairs of sides and the pair of the angles between those two sides to be congruent.
It is given that one pair of sides are congruent, along with a pair of congruent angles.
We want the congruent angle to be between two congruent sides, thus AC must be congruent to EC in order for these triangles to be proven congruent by the SAS postulate.
Hope this helps and have an awesome day! :)
