Water falling vertically from the mouth of a tap in streamline flow forms a tapering column as shown in the Fig. 12.69. Which of the following is the most correct explanation for this?

As the water falls down, its velocity increases resulting in decrease in pressure. So, it is then compressed by the surrounding air.

The mass of water passing through any cross-section must remain constant. So in accordance with Av = constant (as liquid is incompressible), the area of cross-section decreases with increase in velocity.

Due to surface tension effect, exposed surface area of liquid decreases.

To attain terminal velocity, area of cross-section decreases.