Explanation:

A planar mechanism is a mechanical system that operates in a two-dimensional plane. It consists of a set of rigid bodies (links) connected by joints (revolute, prismatic, etc.). Each link has a certain degree of freedom (DOF) which describes its motion relative to the other links. A mechanism with a single DOF has only one independent variable (angle or distance) that determines the position of all the links.

Higher and lower kinematic pairs refer to the type of joints that connect the links. A higher pair is one in which the two surfaces come into contact and slide relative to each other, while a lower pair is one in which the two surfaces come into contact and roll relative to each other. For example, a revolute joint is a higher pair, while a prismatic joint is a lower pair.

To determine the minimum number of links in a planar mechanism with both higher and lower kinematic pairs, we can use the following approach:

- Start with a single link and add joints to it until we achieve the desired DOF.
- To achieve a single DOF, we need at least one higher pair and one lower pair.
- A higher pair provides one DOF, while a lower pair provides two DOF (one translational and one rotational).
- Therefore, we need to add at least one higher pair and two lower pairs to achieve a single DOF.
- We can achieve this by adding a revolute joint (higher pair) at one end of the link and two prismatic joints (lower pairs) at the other end.
- The revolute joint provides one DOF, while the two prismatic joints provide two DOF in total (one translational and one rotational).
- Thus, we have a planar mechanism with one DOF and three links (one revolute joint and two prismatic joints).

Therefore, the correct answer is option C, i.e., three.

Lowest no of links in a kinematic pair with all lower pairs is 4