Question: I read this background article the other day: All fluids exert pressure like the air inside a tire. The particles of fluids are constantly moving in all directions at random. As the particles move, they keep bumping into each other and into anything else in their path. These collisions cause pressure, and the pressure is exerted equally in all directions. When particles are crowded together in one part of an enclosed space, such as the air particles first entering a tire, they quickly spread out to fill all the available space. That’s because particles of fluids always move from an area of higher pressure to an area of lower pressure. This explains why air entering a tire through a tiny opening quickly fills the entire tire.  I am facing a new situation today: Catherine is throwing her friend a birthday party and is starting to put up decorations. She has finished hanging streamers and now she has to fill the balloons. Having never used a helium tank before, she wants to test how much to fill each balloon.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: If Catherine filled two balloons and one expanded more than the other does the smaller balloon have higher or lower air pressure?
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Answer: lower


I read this background article the other day: As time passes, the number of HIV copies keeps increasing, while the number of helper T cells keeps decreasing. The graph in Figure below shows how the number of T cells typically declines over a period of many years following the initial HIV infection. As the number of T cells decreases, so does the ability of the immune system to defend the body. As a result, an HIV-infected person develops frequent infections. Medicines can slow down the virus but not get rid of it, so there is no cure at present for HIV infections or AIDS. There also is no vaccine to immunize people against HIV infection, but scientists are working to develop one.  I am facing a new situation today: Mike is a physician who treats HIV-infected patients. Today, he is seeing two patients, patient A and patient B. Patient A is infected with HIV, but patient B is not infected with HIV. Mike is trying to figure out how HIV-infected patient is different from the patient who is not infected with HIV.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Which patient has lower chance of developing infections, patient A or patient B?
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Answer: patient B


I read this background article the other day: Rain dissolves fertilizer in the soil. Runoff carries it away. The fertilizer ends up in bodies of water, from ponds to oceans. Nitrogen is a fertilizer in the water. Since there is a lot of nitrogen, it causes algae to grow out of control. Pictured below is a pond covered with algae ( Figure below ). Algae use up carbon dioxide in the water. After the algae die, decomposers break down the dead tissue. The decomposers use up all the oxygen in the water. This creates a dead zone. A dead zone is an area in a body of water where nothing grows because there is too little oxygen. There is a large dead zone in the Gulf of Mexico ( Figure below ). The U.S. states outlined on the map have rivers that drain into the Gulf of Mexico. The rivers drain vast agricultural lands. The water carries fertilizer from these areas into the Gulf.  I am facing a new situation today: Park farm and Fiddle farm provided Red city with tonnes of produce annually. Fiddle farm used and abundance of fertilizers and pesticides, while Park farm didn't use any of those substances.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Which farm caused more fertilizer to end up in ponds?
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Answer:
Answer: Park