The unit of the weight of the body in the MKS system is:

In our everyday life, mass and weight are the terms used interchangeably. But in terms of Science, these two are different things.

Mass is the amount or measure of matter present in a body and is measured in grams or pounds or ounces.

Weight is the force (attractive) exerted on a body by the Earth and is measured in Newtons.

Weight, $\mathrm{W}= \mathrm{mg}$ where ' $\mathrm{m}$ ' is the mass of the body and ' $\mathrm{g}$ ' is the acceleration due to gravity and its unit is N or $\mathrm{kg}.\mathrm{m}/{\mathrm{s}}^2$.

Hence, the correct option is A).