The correct order of storage units from smallest to largest is: * Kilobyte (KB) * Megabyte (MB) * Terabyte (TB) * Petabyte (PB) "A kilobyte is approximately 1,000 bytes. It is smaller than a megabyte (1 million bytes), terabyte (1 trillion bytes), or petabyte (1 quadrillion bytes)." - CompTIA ITF+ Reference Hence, C. Kilobyte is the smallest unit listed.