question: the arc ACB is exactly a semicircle. the water surface width A′B′ in the bridge hole is ()
  Choices:
  A:√{15}m
  B:2√{15}m
  C:2√{17}m
  D:no solution
query_wo: Please directly answer the question and provide the correct option letter, e.g., A, B, C, D.
  Question: the arc ACB is exactly a semicircle. the water surface width A′B′ in the bridge hole is ()
  Choices:
  A:√{15}m
  B:2√{15}m
  C:2√{17}m
  D:no solution
query_cot: Please first conduct reasoning, and then answer the question and provide the correct option letter, e.g., A, B, C, D, at the end.
  Question: the arc ACB is exactly a semicircle. the water surface width A′B′ in the bridge hole is ()
  Choices:
  A:√{15}m
  B:2√{15}m
  C:2√{17}m
  D:no solution
question_for_eval: the arc ACB is exactly a semicircle. the water surface width A′B′ in the bridge hole is ()
  Choices:
  A:√{15}m
  B:2√{15}m
  C:2√{17}m
  D:no solution