Correct Answer - Option 3 : Both 1 and 2
Kinematic Pair: If two links are connected anyway then they form a pair, but this pair will also be kinematic pair if the relative motion between the links is constrained to motion.
Kinematic Chain: If the links are connected in such a way that the first link is connected to the last link in order to get the closed chain and if all the relative motions in this closed chain are constrained then it is known as a kinematic chain.
Degree of Freedom: The degree of freedom (DOF) of a mechanical system is the number of independent variables required to define the position or motion of the system.
For a simple mechanism, the degree of freedom (F) is given by the Grubler’s criterion:
F = 3 (n - 1) - 2j - h
Where j = number of revolute joints
n = number of links
h = number of higher pairs