Which of the following is the largest: Astronomical Unit,Light Year,or Parsec?

What is a unit? What are fundamental units and derived units?

$A$ micron is related to a centimetre as:

Density of wood is $0.5 \, g/cm^3$ in the $CGS$ system of units. The corresponding value in $SI$ $(MKS)$ units is ........... $kg/m^3$.

An ice cream has a marked value of $700 \, kcal$. How many kilowatt-hour $(kWh)$ of energy will it deliver to the body as it is digested?

The $SI$ unit of length is 'metre'. Suppose we adopt a new unit of length which equals $x$ metre. Then,the area of $1 \ m^2$ expressed in terms of the new unit has a magnitude of: