The correct answer is 1 - 100 nm.

  Key Points

• Nanoparticle ,ultrafine unit with dimensions measured in nanometres (nm; 1 nm = 10−9 meter).
• Nanoparticles exist in the natural world and are also created as a result of human activities .
• The nanoparticle of their submicroscopic size  has unique material characteristics.
• Manufactured nanoparticles may find practical application s in various  areas , including medicine ,engineering ,catalysis , and environmental remediation .
• Nanoparticles can be classified into  various types , according to their size ,shape , and material properties .

  Additional Information

• Properties of Nanoparticles:
  • In 2008 the International Organization for Standardization (ISO) defined a nanoparticle as a discrete nano-object where all three Cartesian dimensions are less than 100 nm.
  • Nano-object needs only one of its characteristic dimensions to be in the range 1–100 nm to be classed as a nanoparticle , even if its other dimensions are.
  • Size range from 1 to 100 nm overlaps considerably with that previously assigned to the field of colloid science from 1 to 1,000 nm  which is sometimes alternatively called the mesoscale.