Answer: The ratio of the number of oxygen molecules to the number of nitrogen molecules in these flasks is 1: 1
Explanation:
According to avogadro's law, equal volumes of all gases at same temperature and pressure have equal number of moles.
According to avogadro's law, 1 mole of every substance contains avogadro's number 
of particles.
Thus as oxygen and nitrogen are at same temperature and pressure and are in equal volume flasks , they have same number of moles and thus have same number of molecules.
The ratio of the number of oxygen molecules to the number of nitrogen molecules in these flasks is 1: 1
Sorry this will probably be pretty long.
So think of the "control" as being something you yourself add to increase or decrease the effects in an experiment.
I'll give you an example so it is not as confusing.
Say you have decided to make an experiment on plants. Which plant can grow the fastest on which type of liquid? What is being added to this experiment? The liquid! Or all of the liquids you used. Like if you used Coke, Lime Gatorade, Orange Gatorade, and Water. Each drink will EFFECT each plant differently.
Hope I was of any hope?
True energy passes from animal to animal or plant to plant
The correct answer is the first choice given. Plants and algaes are producers. They are called as such since they produce their own food by using the energy from the sun, CO2 and water to form glucose as their food.
