5. Given the figure's markings and $m \angle A=76^{\circ}$ and $m \angle B=104^{\circ}$ whichtheorem can be used to prove that the quadrilateral is a parallelogram?
Theorem 33
Theorem 34
Theorem 35
Theorem 36
Not a parallelogram

Step 1 ：Given the figure's markings and \(m \angle A=76^{\circ}\) and \(m \angle B=104^{\circ}\), we are asked to identify which theorem can be used to prove that the quadrilateral is a parallelogram.

Step 2 ：In a parallelogram, opposite angles are equal. However, the angles given are not opposite angles, they are adjacent angles.

Step 3 ：The sum of adjacent angles in a parallelogram is 180 degrees. Therefore, if the sum of the given angles is 180 degrees, we can use this to prove that the quadrilateral is a parallelogram.

Step 4 ：Calculating the sum of the given angles, we find that \(76^{\circ} + 104^{\circ} = 180^{\circ}\). This means that the given angles are supplementary, which is a property of adjacent angles in a parallelogram.

Step 5 ：Thus, we can use this property to prove that the quadrilateral is a parallelogram. The theorem that states that if the consecutive angles of a quadrilateral are supplementary, then the quadrilateral is a parallelogram, can be used.

Step 6 ：Final Answer: \(\boxed{\text{Theorem 34}}\)