Independent variable would be salt since you can't change it in this experiment.
C because first comes the source or producer than the first eater then the second and then it decomposes
Are you kidding me is this answer or question you got be kidding
Answer is Mr and S as MgS ..
Answer : The molecule
is a polar molecule.
Explanation :
Polar molecule : When the arrangement of the molecule is asymmetrical then the molecule is polar.
Non-polar molecule : When the arrangement of the molecule is symmetrical then the molecule is non-polar.
The given molecule is, 
The electronegativities of oxygen and fluorine are different. The molecular geometry of
is bent. As, Fluorine is more elctronegative than the oxygen. So, the arrows putting towards the more electronegative element i.e, fluorine. These arrows do not balance each other. Due to this, the asymmetrical arrangement of these bonds makes the molecule polar.
Hence, the given molecule
is polar.