Manometers can be specifically used to measure what kind of pressure?

Manometers are devices used to measure pressure in fluids and are particularly versatile in measuring both positive and negative pressures. Unlike some instruments that are limited to measuring absolute pressure or only specific variations, manometers can accurately reflect changes in pressure, whether the fluid pressure is above or below the atmospheric pressure. This feature allows them to effectively capture a wide range of pressure values, including scenarios when fluids are under vacuum (negative pressure) or when they are pressurized (positive pressure).

The functionality of manometers hinges on the principle of liquid columns, where the height difference in the liquid (usually a specific fluid like mercury or water) corresponds to the pressure difference being measured. Therefore, they can be essential tools in applications where distinguishing between various pressure states is necessary, such as in HVAC systems, laboratories, and various industrial processes.

While the other choices focus on particular types of pressure readings—absolute pressure being measured against a perfect vacuum, variable atmospheric pressure being dependent on changes in the environment, and static pressure referring to pressure in a system at rest—these do not encapsulate the complete functionality of a manometer. The ability to capture both positive and negative pressure makes option B the most comprehensive and accurate choice in this context.