Limit of Proportionality on Spring Graph

Steps:

• Recall Hooke's law: extension (x) is proportional to load (F), so graph is a straight line through origin.
• Examine graph for straight-line region from origin.
• Identify deviation point where curve begins, ending proportionality.
• Select point at end of straight line as limit.

Why B is correct:

• B marks end of straight-line portion, where extension ceases to be directly proportional to load per Hooke's law (F = kx).

Why the others are wrong:

• A: Lies within straight-line region, so still proportional.
• C: On curved portion, beyond proportionality limit.
• D: Further on curve, showing plastic deformation.

Final answer: B