PrepTest 122 - Section 3 - Passage 4 - Question 24

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Every culture that has adopted the cultivation of maize—also known as corn—has been radically changed by it. ███

intro topic · Influence of maize

explain significance · of maize

Contributed to development of agrarian and urban societies, and European population growth

hypothesis · Maize's influence is due to its productivity

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phenomenon · Productivity of maize

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Intro to hypothesis · Biochemistry provides the answer

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Context · Explanation of photosynthesis

Water splits into hydrogen and oxygen, hydrogen produces energy. Meanwhile, carbon dioxide builds sugars with help from enzyme (rubisco).

Problem · Too much oxygen interferes with photosynthesis

Enzyme supposed to work with carbon dioxide, but oxygen binds to enzyme instead, meaning less enzyme available to work with carbon dioxide

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Solution (hypothesis) · Different method of photosynthesis

Enzyme (rubisco) is kept separate from atmospheric gases (e.g., oxygen and carbon dioxide)

Complication with hypothesis · Carbon dioxide cannot reach enzyme as gas

Solution: Carbon dioxide becomes nongas molecule (C-4) in order to reach enzyme and drive photosynthesis

Strengthen hypothesis · Other highly productive crops use this method of photosynthesis

Passage Style

Phenomenon-hypothesis (RC)

Single position

24.

The author's reference to " ███ █████ ███████████ ██████ ████ ███ ██████ ██ ███ ████ █████████ █████ █████ ███ ██ ███ █████████ █████ ██ ███ ████████

Question Type

Purpose in context (of word, phrase, or idea)

Structure

This asks for the purpose of a phrase in the broader context of the passage. The phrase tells us that in C-4 plants, oxygen isn't the only gas kept away from rubisco; other gases are, too. This sets up a problem: how does carbon dioxide, which is important for photosynthesis, react with rubisco? The author then immediately sets about explaining how C-4 plants overcome that problem. So the purpose of the phrase is to introduce a problem and and then explain its solution.

It indicates why ███████ ███████████ ██████████ ███ █████ ██████ ██████ ██ █████ ██ ███ ████ ██████ ██████████████ ██ ███████ ██████ ██ █████████ ██ ███ ████████ ██████████

The reference to “all other atmospheric gases” only applies to what’s going on in C-4 plants. It has nothing to do with non-C-4 plants. In fact, the author never does explain why “common atmospheric conditions” can cause oxygen to build up and hinder photosynthesis in non-C-4 plants.

14%

It supports the █████ ████████ ███████ ██ ███ █████████ ████ ██████ ██ ███ ███ ████ ███████████ ███ █████ ████████ ██ ███ ████ ███ █████████ ████ ███████████████

This claim is never made in the passage. The only gases discussed are oxygen, hydrogen, and carbon dioxide—and of the three, only oxygen is identified as interfering with photosynthesis. Hydrogen and carbon dioxide, meanwhile, are both beneficial for photosynthesis.

27%

It supports the ██████████ ████ ███████ ██████████████ █████ ███ ██ ███████ ███████████ █████ ████ ███ ██████████████ ████ ███ ████

The author doesn’t reach this conclusion. She never suggests that C-4 and non-C-4 plants differ in which gases they use. Rather, she indicates that both types of plant make use of the same gases: hydrogen and carbon dioxide. Her conclusion, meanwhile, is that C-4 plants are different because of their ability to shut out oxygen gas, which neither C-4 nor non-C-4 plants make use of.

It explains why ██████ ███████ █████████ ███████ ███ ███████████████ █████████ █████ ██ ███ █████████ ██████ █████████████ ██ ██████████████ ██ ███ ███████

It first raises a problem: if “all other atmospheric gases are excluded,” then carbon dioxide can’t reach rubisco as a gas. The existence of this problem, in turn, explains why C-4 plants have had to develop a solution: carbon dioxide undergoes a series of transformations in order to covert it to a non-gaseous form, allowing it to reach rubisco and participate in photosynthesis.

48%

It advances a ███████ █████ ████ ██████ ██████ ██████ ████████ ██ ███ ██████ ██ █████ ██ ███████ ██ ███████████ ███████████

The author doesn’t make this claim. She never suggests what the oxygen levels might look like in C-4 plants. Rather, she just indicates that oxygen is present to some extent (due to the splitting of water) and then focuses on how oxygen is kept physically separated from rubisco.

PrepTest 122 - Section 3 - Passage 4 - Question 24

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