Step 1: Concept
A piezometer is the simplest form of a manometer, consisting of a vertical tube.
Step 2: Meaning
One end is connected to the point where pressure is to be measured, and the other end is open to the atmosphere.
Step 3: Analysis
It measures the "static" pressure (the pressure exerted by the fluid when not considering its motion) by observing how high the liquid rises in the tube due to its internal pressure.
Step 4: Conclusion
It measures the static pressure of the fluid.
Final Answer: (C)