Students noticed that some of their classmates have a hard time concentrating during class. they thought
it may have some connection with the fact that these students consume energy drinks just before class. an
experiment was proposed to find out if there is a connection between energy drinks and the lack of ability
to concentrate in class. a properly designed experiment to determine this would include having
(1) the whole class drink energy drinks and no water at all, for the entire time of the experiment
(2) the whole class drink water and no energy drinks at all, for the entire time of the experiment
(3) the students drink both water and an energy drink just before class
(4) half the students drink water and the other half drink an energy drink just before class
note: the answer to question 75 should be recorded on your separate answer sheet.

It would be (4), because that's the only option in which you are able to compare the two different drinks. Drinking only one would provide no comparison to the other, and having them drink both would 'contaminate' the investigation, and you wouldn't know under which effect the person was reacting to (Water or energy drink)

Pt.I

All living things needs some form of oxygen to live. In talking about a scuba diver, we are talking about a human, who uses their lungs to breathe, and did not develop the ability to breathe under water. Instead, when in a body of water, we tend to hold our breaths until an opportunity arises for us to exchange our carbon dioxide for oxygen.

Take into account the scuba gear. The scuba gear fits the user, and has a number of protection, including the suit counter-balancing any pressure applied by the deep, and the tank providing much needed oxygen to the user during delayed periods within the water.

Pt.II

How does these two systems interact?

Like as a human is breathing on land or even swimming, the human expels carbon dioxide, which forms into "air bubbles" that are then expelled into the water surrounding. The user then draws air from the pressurized air tank, and is able to breathe as such. This allows the user to stay underwater for much longer than just one breathe, and is able to travel farther inside the deep.

Inside this system, the Oxygen is first input into the oxygen tanks, which are then used by the diver. The diver would draw the oxygen from the tank (output), and he will then expel the used air into the surrounding water.

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