A gas. This is because none polar solvents contain binds between atoms with similar electronegativities, some examples are carbon and hydrogen
The independent variable is what will change. The dependent variable is what will change because of the independent variable. The controlled variable is what will stay the same.
Ex, for the first one.
IV: the amount of sunlight
DV: plant growth
CV: pea plant
For #2.
IV: the soda
DV: the amount of sugar
CV: soda
And so on
The volume is mass density is h,w,l