{
  "correct_letter": "B",
  "correct_formula": "ΣM_ext = 0",
  "annotation": "Environment: g=9.81, F_drag=!=0",
  "choices": [
    "W = ΔE_k = (1/2)·m·v_t² - (1/2)·m·v_0²",
    "ΣM_ext = 0",
    "ΣF = m·Δv / (Δt·cosθ)",
    "B = μ_0·I / (2π·r)"
  ],
  "correct_index": 1,
  "physics_type": "AtRest",
  "seed": "AtRest|NewtonsFirstLaw/AtRest/9",
  "is_realworld": true,
  "dropped_wrong_formulas": [
    "F_drag = (1/2)·C_d·ρ·A·v²"
  ]
}