2. According to the unit conversion of meters at all levels, we can know that: 1 km =1000m (m) =10000m (DM) =100000m (cm).

3. The meter is the basic unit of the international system of units. The International System of Units * * * has seven basic units, namely, length m, time s, mass kg, thermodynamic temperature (Kelvin temperature) k, current a, light intensity cd (Candeira), and quantity mol of matter.