Jawaban:

The diagram depicts a situation where a boy is blowing air into a glass using a rubber hose. The air is being blown from the boy's mouth through the rubber hose into the glass.

As the boy blows air into the glass, the water level inside the glass will decrease or go down. This happens because the increase in air pressure inside the glass pushes the water down.

When the boy blows air into the glass, the pressure inside the glass increases. This increase in pressure forces the water level to decrease as the air pushes against the surface of the water. Essentially, the higher pressure of the air displaces the water and causes it to move down.

This phenomenon is a result of Boyle's Law, which states that when the volume of a gas (in this case, the air blown into the glass) increases at a constant temperature, the pressure of the gas decreases. Similarly, when the volume of a gas decreases, the pressure increases. In this case, as the boy blows air into the glass, the volume of the air increases, causing the pressure inside the glass to rise and consequently pushing the water level down.

It's important to note that this explanation assumes that the air blown into the glass does not escape and remains sealed inside, exerting pressure on the water.