The controlis the plant with just water. The independent variable is the plants. The dependaent is the amout of salt in the water.
The indepedent is the trees. The dependent is the greenhouse or no greenhouse.
Answer:
I am positive the answer is C because I used to study the exact same lesson.
The aveoli opens and closes to allow the oxygen in but keep out food liquids any thing that's not a gas bacicaly
