How many fundamental base units form the International System of Units (SI)?

### Why this is right The International System of Units (SI) is built on seven fundamental base units. These units provide the starting standards from which other measurements can be derived. ### The concept The seven units correspond to length, time, mass, temperature, amount of substance, electric current, and luminous intensity. Biophysics uses these standards to measure biological processes at molecular, cellular, and physiological scales. ### The other options - **A. Five**: fewer than the seven base units specified in the SI system. - **B. Six**: also omits one of the seven base units. - **D. Ten**: confuses the base-unit count with the many derived units and metric prefixes used in science. ### Terms - **International System of Units (SI)**: the globally agreed system of scientific measurement. - **Base unit**: a standard unit for a fundamental quantity. ### Remember The SI system has seven base units.