The SI unit for the amount of substance is: 

CONCEPT:

SI Unit for the Amount of Substance

• The International System of Units (SI) provides a standard set of units for measurements used worldwide. It ensures consistency and uniformity in scientific communication and calculations.
• The SI unit for the amount of substance is called the "mole (mol)".
• A mole is defined as the amount of substance that contains as many elementary entities (e.g., atoms, molecules, ions, electrons) as there are atoms in 12 grams of pure carbon-12 isotope. This number is known as the Avogadro constant, approximately equal to 6.022 × 10²³.

EXPLANATION:

• Kilogram—This is the SI unit of mass.
• Gram - This is not an SI unit but a derived unit for mass.
• Mole - This is the correct SI unit for the amount of substance.
• Candela - This is the SI unit for luminous intensity.
• Therefore, the correct answer is Option 3: Mole.

Hence, the SI unit for the amount of substance is the mole (mol).