Which statement about SI units is correct?

• A. They are used worldwide and include units for time, length, mass, electric current, thermodynamic temperature, amount of substance, and luminous intensity
• B. They are a regional standard used only in North America
• C. They exclude units for temperature
• D. They are the same as CGS units

Answer: (A)

SI units are the internationally adopted system for measurements, defined by seven base quantities and their units. These base quantities are length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity, with corresponding base units of meter, kilogram, second, ampere, kelvin, mole, and candela. The statement lists exactly these seven quantities, showing that SI covers time, length, mass, electric current, temperature, amount of substance, and luminous intensity. SI is used worldwide as the standard, not limited to a region. Temperature is included (in kelvin), and SI is distinct from CGS, which uses different base units like centimeter and gram.