What else would need to be congruent to show that abc def by aas?

The correct answer is A. ∠A = ∠D

Step-by-step explanation:

To prove any two triangles congruent by using the AAS congruency postulate we need to show corresponding two angles and one corresponding side of the two triangles are equal.

Now, to show ΔABC ≅ ΔDEF by AAS congruency postulate,

∠ACB = ∠DFE = 30° ( From the given figure)

∠ABC = ∠DEF ( It should be equal if the triangles are to proved congruent by AAS rule)

AB = DE = 10 units ( From the given figure)

So, ΔABC ≅ ΔDEF by AAS congruency rule.

Hence, The correct answer is A. ∠A = ∠D