TOEFL Reading Practice Test #36

The correct answer is A. The word "components" refers to the basic parts or elements that make up something—in this case, the parts that make up cells. "Bodies" is incorrect because it usually refers to whole structures or organisms, not individual parts. "Combinations" implies mixtures or groupings of elements, which is not the intended meaning here. "Characteristics" refers to traits or features, not physical parts, so it is also incorrect.

The correct answer is A. The passage explains that heavy elements are made in stars and spread by stellar deaths, and it uses this information to support the idea that life-essential elements are widely distributed. The passage does not discuss the relative age of our solar system, so B is incorrect. While some older star systems may have fewer heavy elements, the main purpose is not to compare their likelihood to support life, making C incorrect. D is wrong because the passage does not focus on the reason for the mass difference between elements.

The correct answer is C. The paragraph says heavy elements increase over time, so newer systems would contain more heavy elements. A is incorrect because the passage never compares the quantity of planetary bodies across star systems. B is incorrect because hydrogen and helium are consistently dominant in all systems. D is wrong because the passage suggests that the formation process remains the same, regardless of age.

The correct answer is B. The key idea in the original sentence is that planetesimals are made of heavy elements because hydrogen and helium remain gaseous and don’t condense into solids. A is wrong because it wrongly implies hydrogen and helium combine with heavy elements to form planetesimals. C is incomplete; it misses the explanation about hydrogen and helium staying gaseous. D is incorrect because it falsely says that planetesimals contain gases, when the original says gases don’t condense into them.

The correct answer is D. The paragraph clearly says most biologists think life elsewhere is also likely to be carbon based. A is incorrect because the passage mentions silicon- or nitrogen-based life as a possibility. B is not mentioned at all and is irrelevant. C is incorrect because the paragraph emphasizes that all life, no matter its chemical basis, would still use elements formed in stars.

The correct answer is C. The paragraph suggests that organic molecules are widespread and possibly similar across planets due to common delivery methods, so claiming they were significantly different is incorrect. A is true according to the paragraph. B is also stated directly. D is correct because the text mentions amino acids and complex molecules.

The correct answer is B. The passage says molecules stay intact beneath surfaces, meaning they remain whole or undamaged. “Buried” is incorrect because it refers to position, not condition. “Confined” means restricted in movement or space, which doesn’t match the context. “Active” means capable of action, which also doesn’t apply.

The correct answer is C. The passage explains that without a liquid or gas, organic molecules likely can’t interact because they can’t move. A is wrong because the passage says molecules are destroyed by solar radiation on unprotected surfaces—not by lacking a liquid. B is incorrect; asteroid impacts are said to be widespread. D misrepresents the threat, which comes from radiation, not asteroids or comets.

The sentence “To answer the question ‘Could life exist on other planets?’ we must first look at the necessary preconditions for life” introduces the main theme of the passage, which is the search for life elsewhere in the universe based on the chemical requirements for life.

It works best at position [1] because it provides a natural lead-in to the rest of the paragraph, which begins discussing what life needs in terms of chemical elements. Placing the sentence here sets up the purpose of the discussion and makes the logical flow of ideas clearer.

Placing the sentence at [2], [3], or [4] interrupts the explanation of what those elements are and how they are used in life on Earth. These later placements feel awkward because they shift focus mid-paragraph, after the topic has already begun to unfold.

The correct answers are B, D, and F. B supports the idea that the common elements used by life are abundant throughout the universe. D explains that all bodies formed from planetesimals contain the elements needed for life. F adds that for organic molecules to react, a certain environment is required—important for the development of life.

A is too specific and not emphasized. C is incorrect because the passage says older systems may actually have fewer heavy elements. E is wrong because the passage says all bodies were hit by comets and asteroids.