To express all the physical quantities in SI units, we need:
(A) two fundamental units
(B) three fundamental units
(C) five fundamental units
(D) seven fundamental units

Hint: Every physical quantity is having the SI units; the SI units are used to express the physical quantities in the easy way. In physics, each and every quantity is expressed in the SI units or fundamental units, these units are used to express the quantities.

Complete step by step solution:
In general, there are seven basic fundamental units, they are length, time, amount of substance, electric current, temperature, luminous intensity and mass. Each and every fundamental unit is having the units. For length is meter, for time is seconds, for the amount of substance is mole, for electric current is ampere, for temperature is kelvin, for luminous intensity is candela and for mass is kilogram. These are the units of the fundamental units.
The SI units are the standard units which are used to express the physical quantity. And some of the fundamental units are having other units also. For example, temperature is expressed in Kelvin, Celsius and Fahrenheit, and the mass is expressed in kilogram and gram, and the length is expressed as meter, kilometer, centimeter, milli metre and etc. and the time is expressed in seconds, minutes hours and milliseconds.
The SI units are called the international system of Units, are the international standards to measure. All the countries which are signed in the international treaty of the meter are using these SI units for the measurements.

Hence, the option (D) is the correct answer.

Note: The SI units are the seven base units and from these seven base units twenty-two units are derived. The SI units play an important role in international commerce and are commonly used in the technology and scientific research and development.