which pair of angles is complementary?

Explanation:

Step1: Recall complementary - angle definition

Two angles are complementary if their sum is 90°.

Step2: Check the first pair

$31^{\circ}+69^{\circ}=100^{\circ}\neq90^{\circ}$

Step3: Check the second pair

The right - angled symbols are not relevant to the angle - sum check. But we focus on the non - right - angled pairs.

Step4: Check the third pair

$56^{\circ}+34^{\circ}=90^{\circ}$

Answer:

The pair of angles with measures 56° and 34° is complementary.