text: A<unk>  (American spelling:<unk> r, symbol<unk>  (Greek: νάνος, nanos, dwarf; μετρώ, metrό, count) is a unit of length in the metric system, equal to one billionth of a metre (i.e., one millionth of a millimetre), which is the current SI base unit of length. It can be written in scientific notations as 1×10−9 m (engineering notation) or 1 E-9 m (exponential notation) — both meaning 1/1,000,000,000 metres.
  femtometre <<< picometre <<<<unk>  <<< micrometre <<< millimetre < centimetre < decimetre < metre < decametre < hectometre < kilometre
  It is one of the more often used units for very small lengths, and equals ten Ångström, an internationally recognized non-SI unit of length.  It is often associated with the field of nanotechnology. Formerly, millimicron (symbol mµ) was used for the<unk> .
  It is also the most common unit used to describe the manufacturing technology used in the semiconductor industry. It is the most common unit to describe the wavelength of light, with visible light falling in the region of 400-700nm.
option_0: Nanometre
option_1: Liter
option_2: Electronvolt
option_3: Molar 
option_4: Meter
option_5: Rape
option_6: DNA
option_7: Sole 