Final answer:
To prove triangle congruence by the SSS postulate, all three pairs of corresponding sides must be congruent, not the angles.
Step-by-step explanation:
To show that triangles EFG and JKL are congruent by the Side-Side-Side (SSS) postulate, we would need to demonstrate that all corresponding sides of the two triangles are congruent. This means that if two triangles already have two pairs of sides that are known to be congruent, the third pair must also be proven congruent to satisfy the conditions of SSS congruence. Therefore, the correct answer to what else would need to be congruent is b. Corresponding sides. The SSS postulate does not require any angle measurements to prove triangle congruence.