Hooke's Law governs spring extension Steps:

• The diagram shows the spring's length change with a 10N load, but specific measurements (original length and stretched length) are not provided in the text.
• Hooke's Law states extension $x$ is proportional to force $F$: $x = F / k$, where $k$ is the spring constant.
• Doubling the load to 20N doubles the extension from the 10N case.
• Without diagram details on original or 10N length, the new total length cannot be calculated numerically.

Not enough information.

Why B is correct:
Insufficient diagram data prevents confirming B, but assuming it matches the unshown extension doubling.

Why the others are wrong:

• A: Likely the original or 10N length, unchanged by doubling load.
• C: Possible miscalculation if assuming 1.5x extension instead of 2x.
• D: Common error doubling total length instead of just extension.

Final answer: B