Name a pair of congruent:

a. acute angles

b. right angles

c. obtuse angles

Congruent angles are the angles that have equal measures.

Acute angles are the angles which measures between $\mathbf{0}\mathbf{°}$and $\mathbf{90}\mathbf{°}$.

From the figure, it can be observe that $\angle AOB$and $\angle HOG$are both congruent and acute angles, that is, both measures $20°$and is less than $90°$.

Therefore, a pair of congruent acute angles is $\left(\angle AOB,\angle HOG\right)$.

Congruent angles are the angles that have equal measures.

Right angle is an angle which measures exactly $\mathbf{90}\mathbf{°}$.

From the figure, it can be observe that $\angle AOC$and $\angle COH$are both congruent and right angles, that is, both measures exactly $90°$.

Therefore, a pair of congruent right angles is $\left(\angle AOC,\angle COH\right)$.

Congruent angles are the angles that have equal measures.

Obtuse angles are the angles which measures between $\mathbf{90}\mathbf{°}$and $\mathbf{180}\mathbf{°}$.

From the figure, it can be observe that $\angle AOG$and $\angle HOB$are both congruent angles and obtuse angles that is, both measures $160°$and are less than $180°$.

Therefore, a pair of congruent obtuse angles is $\left(\angle AOG,\angle HOB\right)$.