The SI unit of weight is: 

We are aware that a body's weight is the force of gravity acting on the object. And its SI reflects the newton of power. The SI unit of mass is Kg, as we can thus see. Following that, we observe that the tone and pound are additional mass units that are $1tonne=1000Kg and 1pound\left(lb\right)=0.4359Kg.$

1. The gravitational force pulling on an item is measured by its weight.
2. The weight of the body on the ground is equal to the force pulling it toward the earth.
3. The mass is what determines it $F=m.g$
4. It also depends on the object's steady gravitational acceleration toward the earth.
5. The weight-finding equation, 

where m is the object's mass, F represents force or weight, and g is the acceleration brought on by gravity.

6. Since weight is a kind of force, the SI unit for it is the newton.

Hence, the correct answer is option C.