PSAT Writing and Language Practice Test 48: Carbon

Questions 1-11 refer to the following information.

Carbon

You can burn me for energy or find me in plastics. When I am soft, pliable, and dark, I am used to write with. When I am diamond shaped and clear, I go on your left hand. I might be in your stocking or your gas tank, and I always show up to the family barbecues. I make up 1 2% of the human body, forming the basis of your very DNA. I am life when mixed with oxygen but death without enough of it. 2 It takes a lot to melt me, my nature is quite unreactive. With an atomic number of 6 and a weight of 12.011, I am the fourth most common element in the entire universe. I'm all about the bonds, attaching to up to four atoms at one time. 3 Chemists, casually refer to me as the basis of all plant and animal life, so you could say I have some big footprints to fill. 4

If you guessed iron, you're wrong. If you guessed nitrogen, you are equally incorrect. 5 Sulfur, lacking in many of the characteristics of other atomic elements, is not suitable for this purpose. Carbon is the name; living organisms are the game. And it just so happens that I form more compounds than any other element, making me a building block of life on Earth. You might 6 have heard of my most common isotope, carbon-12, because it occurs naturally and makes up 99% of the carbon on your planet. If you happen to be more versed in the wonders of the chemical world, you might recognize me as the basis of graphene, a material stronger than steel but more flexible than rubber.

[1] My versatility is both gift and curse. [2] When I can find two oxygen atoms, I make carbon dioxide, which is found in Earth's atmosphere and used in photosynthesis. [3] Carbon footprint refers to the amount of greenhouse gas emissions generated by a particular country, organization, etc., and damages to Earth's ozone layer. [4] Hence, carbon dioxide—essential to life—can be detrimental in excess quantities. [5] 7 Accordingly, when I join with only one oxygen atom, I form a toxic gas known as carbon monoxide and 8 are responsible for fatal poisonings. 9

For millions of years, I operated 10 between a balanced cycle. Plant life extracts me from the atmosphere in large quantities for food and energy, and I return to the atmosphere through respiration, 11 decomposing, and combustion. But humans disrupted my cycle by burning fossil fuels at rapid rates and destroying forests and plant life. Since I'm so critical to life, you may want to be more careful in the future.