24.The students were over the problem listening to the teacher with a expression on th

问题补充：

24.The students were over the problem, listening to the teacher with a expression on their faces.

A. puzzled; puzzling; puzzling

B. puzzled; puzzling; puzzled

C. puzzling; puzzling; puzzled

D. puzzling; puzzled; puzzling

答案：

A. puzzled; puzzling; puzzling

(答案→)B. puzzled; puzzling; puzzled

C. puzzling; puzzling; puzzled

D. puzzling; puzzled; puzzling

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