Explanation:

- Statement 1: This is correct. Nanotechnology involves manipulating materials on an atomic or molecular scale, essentially creating materials and devices atom-by-atom.

- Statement 2: This is correct. At the nanometer scale, materials can exhibit different physical properties, such as increased strength or altered magnetic properties.

- Statement 3: This is also correct. Chemical properties can change at the nanoscale due to the increased surface area and quantum effects, affecting reactivity and other characteristics.

Correct Answer: Option:4 i.e.1, 2 and 3