Answer:
3rd Option is correct.
Explanation:
Given: A circle with Center is O.
Figure is also Given.
To find: Tangent to the circle.
Tangent is a line which just touches circle at one point and passes from outside of circle.
Option 1).
Segment OP is radius of the circle. It is in interior of the circle.
Thus, This is not Tangent.
Option 2).
line ST is Secant to the circle as it passes through circle and intersect at two points. It is in interior of the circle and also in exterior of circle.
Thus, This is not Tangent.
Option 3).
Line MN is Tangent according to the definition of Tangent.
Thus, This is Tangent.
Option 4).
Segment QR is chord of the circle. It is in interior of the circle.
Thus, This is not Tangent.
Therefore, 3rd Option is correct.