Free fall requires only gravity acting, with no air resistance or other forces.

Steps:

• Identify free fall as motion where net force is gravity alone, so acceleration equals g (9.8 m/s² downward).
• Eliminate options with additional forces like drag or tension that reduce acceleration below g.
• Confirm vacuum eliminates air resistance for ideal free fall.
• Select the scenario matching pure gravitational acceleration throughout descent.

Why B is correct:

• In a vacuum, no air resistance acts on the feather, so Newton's second law (F = mg, a = g) applies constantly.

Why the others are wrong:

• A: Bungee cord exerts upward tension after stretching, varying acceleration from g.
• C: At terminal velocity, drag equals weight, net force zero, so acceleration is zero.
• D: Air resistance opposes gravity, reducing net acceleration below g after initial fall.

Final answer: B