Q. A u-tube with constant cross section is partly filled with water. Engine oil of density 0.8g/cm3 is poured into the right arm (without mixing) until the water level rises 2.0cm. The length of the oil column is then:
A. 2.25 cm
B. need to know the cross-sectional area of the U-tube
C. 5cm
D. 6cm
E. 8cm