What is the independent variable?

It is a variable that stands alone and isn't changed by the other variables.

Explanation:

For example; someone's age might be an independent variable. Other factors such as ( what the eat, where they go) aren't going to change a person's age.

and after water is usually warmed by the sun the water temperature raises and then evaporates .

the answer is c. it will give up it's valence electron to the other atom.