50. 洋流又稱海流，依成因性質可分為吹送流(Drift Current)、密度流(Density Current)、傾斜流(Incline Current)、補償流(Compensation Current)，如受恆定風向吹送的北太平洋洋流係屬？ (A)吹送流(Drift Current) (B)密度流(Density Current) (C)傾斜流(Incline Current) (D)補償流(Compensation Current)