Kinematic pairs — the statement “When the connection between two elements is such that only the required kind of relative motion occurs, it is known as a self-closed pair” is:

Introduction / Context: Self-closed (form-closed) pairs use geometric form to constrain relative motion without external forces. Understanding this helps distinguish reliably constrained mechanisms from those that rely on springs or gravity (force-closed).

Given Data / Assumptions:

• Self-closed (form-closed) = constrained by shape.
• Force-closed = requires external force (e.g., spring) to maintain contact.

Concept / Approach: In a self-closed pair, mating profiles (e.g., a pin in a slot, a dovetail, a revolute pair) inherently restrict motion to the intended DOF. The definition in the prompt aligns with standard terminology: the geometry alone enforces the “required kind” of motion.

Step-by-Step Solution:

Verification / Alternative Check: Textbook definitions (theory of machines) confirm form-closed pairs provide constraint by contact geometry alone.

Why Other Options Are Wrong:
Wrong — would contradict the standard definition of self-closed (form-closed) pairs.

Common Pitfalls: Mixing self-closed with force-closed; assuming any contact maintained by a spring is self-closed—it is not.

Final Answer: Right.