What is the correct symbol for the SI unit of time?

The correct symbol for the SI (International System of Units) unit of time is "s," which stands for "second." The second is the base unit of time in the SI system, defined based on the vibrations of cesium atoms. It is a fundamental unit used universally in various scientific and engineering contexts to measure time intervals.

The other symbols mentioned represent different units of time but are not the SI base unit. "h" stands for hours, a commonly used unit that is larger than a second; "min" represents minutes, which is also a derived unit that contains 60 seconds; and "sec" is an informal abbreviation for seconds, but it is not the standard notation prescribed by the SI. Hence, while they may be understood in everyday use, only "s" is the officially recognized symbol in the context of the SI units for time.