Hooke's Law governs spring extension

Steps:

• Recall Hooke's Law: Force F = k * x, where k is spring constant and x is extension.
• Rearrange to x = F / k.
• Substitute F = 7 N, but k is not provided.
• Not enough information to calculate numerical extension.

Why A is correct:

• Cannot verify without k; A may fit if k = 1.67 N/cm (7 / 4.2), but unconfirmed.

Why the others are wrong:

• B: Would require k = 1.25 N/cm, unsupported.
• C: Would require k = 0.467 N/cm, unsupported.
• D: Would require k = 0.35 N/cm, unsupported.

Final answer: Not enough information.