[Q]: United States has varied geographical characteristics. Take for example, the Mississippi Delta. The delta has vast wetland that gets inundated every year. On the contrary, farther west, the Mojave Desert in Nevada sees very little precipitation or floodwater. Both places are beautiful in their own right, and attract many tourists every year. In which place less metal ions would precipitate, Mississippi Delta or Mojave Desert? Hint: When soil is flooded, hypoxia develops, as soil microorganisms consume oxygen faster than diffusion occurs. The presence of hypoxic soils is one of the defining characteristics of wetlands. Many wetland plants possess aerenchyma, and in some, such as water-lilies, there is mass flow of atmospheric air through leaves and rhizomes. There are many other chemical consequences of hypoxia. For example, nitrification is inhibited as low oxygen occurs and toxic compounds are formed, as anaerobic bacteria use nitrate, manganese, and sulfate as alternative electron acceptors. The reduction-oxidation potential of the rhizhosphere decreases and metal ions such as iron and manganese precipitate. Aerenchyma is a modification of the parenchyma.
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[A]: Mojave Desert

[Q]: Two neighboring towns had different demographics. Hill town had younger inhabitants, most of them in their 30's and 40's. Lake town was inhabited by elderly people, most of them above 65 years of age. Which town had more people with loss of mental function? Hint: Old age begins in the mid-60s and lasts until the end of life. Most people over 65 have retired from work, freeing up their time for hobbies, grandchildren, and other interests. Stamina, strength, reflex time, and the senses all decline during old age, and the number of brain cells decreases as well. The immune system becomes less efficient, increasing the risk of serious illnesses such as cancer and pneumonia. Diseases such as Alzheimer's disease that cause loss of mental function also become more common.
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[A]: Lake

[Q]: Pam and Alice studied Earth's climate and vegetation. Pam studied more about high latitudes (70 to 50N), while Alice studied about lower latitudes (30N to 20S). Which person studied more about alpine tundra? Hint: Alpine tundra occurs at high enough altitude at any latitude. Portions of montane grasslands and shrublands ecoregions worldwide include alpine tundra. Large regions of alpine tundra occur in the North American Cordillera, the Alps and Pyrenees of Europe, the Himalaya and Karakoram of Asia, the Andes of South America, and the Eastern Rift mountains of Africa.Alpine tundra occupies high-mountain summits, slopes, and ridges above timberline. Aspect plays a role as well; the treeline often occurs at higher elevations on warmer equator-facing slopes. Because the alpine zone is present only on mountains, much of the landscape is rugged and broken, with rocky, snowcapped peaks, cliffs, and talus slopes, but also contains areas of gently rolling to almost flat topography.Averaging over many locations and local microclimates, the treeline rises 75 metres (245 ft) when moving 1 degree south from 70 to 50N, and 130 metres (430 ft) per degree from 50 to 30N. Between 30N and 20S, the treeline is roughly constant, between 3,500 and 4,000 metres (11,500 and 13,100 ft).
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[A]: Pam

[Q]: Ken is an avid mountain climber. This year he reached the summits of two mountains, mountain A and mountain B. Mountain A is only 5000 ft tall while mountain B is 15000 ft tall. He has also learned a fun fact that water boils faster and at lower temperature at low atmospheric pressure. In which location Ken would need lower temperature to boil water, mountain summit A or mountain summit B? Hint: Regions on the Earth's surface (or in its atmosphere) that are high above mean sea level are referred to as high altitude. High altitude is sometimes defined to begin at 2,400 meters (8,000 ft) above sea level.[5][6][7] At high altitude, atmospheric pressure is lower than that at sea level. This is due to two competing physical effects: gravity, which causes the air to be as close as possible to the ground; and the heat content of the air, which causes the molecules to bounce off each other and expand.[8]
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[A]:
mountain summit B