单项选择题

A.定子线圈和转子线圈都用水冷却,定子铁芯用空气冷却
B.定子线圈和定子铁芯都用水冷却,转子线圈用空气冷却
C.定子线圈和转子线圈都用空气冷却,定子铁芯用水冷却
D.定子线圈和定子铁芯都用空气冷却,转子线圈用水冷却