{
  "correct_letter": "C",
  "correct_formula": "ΣF_ext = 0",
  "annotation": "Environment: g=-9.81, F_drag=0.0",
  "choices": [
    "G = m·g",
    "ΣF = m·Δv / (Δt·cosθ)",
    "ΣF_ext = 0",
    "U = -G·m_1·m_2 / r"
  ],
  "correct_index": 2,
  "physics_type": "AtRest",
  "seed": "AtRest|benchmark/at_rest/3"
}