Answer: B. [tex]79^{\circ}[/tex]
Step-by-step explanation:
In the given picture, we have a circle with the measure of arc RT=[tex]158^{\circ}[/tex]
Let the center of the given circle be O.
Since, the angle subtended by an arc at the center =measure of arc
Therefore, the angle subtended by an arc RT at the center = [tex]\angle{ROT}=158^{\circ}[/tex]
Also, the angle which is subtended by an arc at the center of a circle is double the size of the angle subtended at any point on the circumference.
i.e.[tex]\angle{ROT}=2\angle{RST}[/tex]
Thus, the measure of [tex]\angle{RST}=\frac{\angle{ROT}}{2}=\frac{158^{\circ}}{2}=79^{\circ}[/tex]
Hence, the measure of [tex]\angle{RST}=79^{\circ}[/tex]
