Answer: C. Carbon

Key evidence: The passage states: “The plant obtains carbon and hydrogen dioxide from the atmosphere; other nutrients are taken up from the soil.” Therefore, carbon is obtained from the atmosphere, not taken up from the soil.

Option analysis:

A. Potassium → Listed among important elements and belongs to nutrients taken up from the soil (“other nutrients are taken up from the soil”).

B. Magnesium → Also listed among important elements and is taken up from the soil.

C. Carbon → Correct; explicitly said to be obtained from the atmosphere.

D. Calcium → Listed among important elements and taken up from the soil.

E. Sulfur → Listed among important elements and taken up from the soil.

LaTeX note (required symbols): Atmospheric sources for carbon are \( \gt \) soil sources for carbon in this passage.

Answer: D. most of the nutrients are bound in compounds

Key evidence: The passage explains: “Much of this potential supply, however, is bound tightly in forms that are not released to crops fast enough to give satisfactory growth. Because of this, the farmer is interested in measuring the available nutrient supply…” This directly matches the idea that nutrients may exist in total, but are not available because they are tightly bound.

Option analysis:

A. they do not know how to obtain all the nutrients → Not stated. The problem is not lack of knowledge, but lack of availability/release speed.

B. ... the soil constrains all the nutrients needed → The passage says total supply is usually high, not “constrained.”

C. the nutrient are in the soil → Too general and does not explain why “available” is preferred.

D. most of the nutrients are bound in compounds → Correct; bound forms are not released fast enough.

E. some of the nutrients are found in the atmosphere → True in general for carbon, but it does not explain the stated farmer preference, which is about bound nutrients and release rate.

LaTeX note (required symbols): Total nutrients in soil can be \( \gt \) available nutrients, but availability is what matters for growth.

Answer: A. the result of chemical analyses

Key evidence: Paragraph three begins with “Overall chemical analyses indicate…” and then reports what those analyses show: total supply is usually high, but much is tightly bound and not released fast enough. The paragraph is organized around what the analyses indicate and the consequence for farmers.

Option analysis:

A. the result of chemical analyses → Correct. It is the main framing idea and supports the rest of the paragraph.

B. the requirements of crop plants → Mentioned, but only as a comparison point; not the main topic.

C. giving satisfactory growth to plants → Appears as a problem (not released fast enough), but it is not the overall topic.

D. measuring the available nutrients supply → This is the concluding implication, but it depends on the earlier “analyses indicate…”; it is not the central topic statement.

E. the abundant of nutrients in the soil → Part of the paragraph, but it is only one result; the paragraph also emphasizes the bound form and availability issue.

LaTeX note (required symbols): The “results” drive the conclusion: evidence \( \gt \) assumption in explaining farmer interest.

Answer: A. Five

Key evidence: The passage says the plant contains “sodium, iodine, and cobalt,” which are “apparently not essential,” and adds, “This is also true of silicon and aluminum.” That makes five elements described as not essential: sodium, iodine, cobalt, silicon, and aluminum.

Option analysis:

A. Five → Correct: \(3\) (sodium, iodine, cobalt) plus \(2\) (silicon, aluminum) equals \(5\).

B. Seven → Not supported by the text.

C. Nine → Not supported by the text.

D. Fifteen → Not supported; far beyond the stated list.

E. Sixteen → This is the total minimum number of elements needed, not the number of “not essential” elements.

LaTeX note (required symbols): The number of non-essential elements \(5\) is \( \lt \) the total needed elements \(16\).

Answer: A. gets

Key evidence: In context, “obtains carbon… from the atmosphere” means the plant receives/acquires carbon from the air. The closest meaning is “gets.”

Option analysis:

A. gets → Correct; best synonym for “obtains” in this context.

B. takes → Could be close, but “gets from the atmosphere” is more natural and less forceful than “takes.”

C. puts → Opposite direction of meaning (placing, not receiving).

D. gives → Reverse meaning (donating, not acquiring).

E. has → Describes possession, not the process of acquiring.

LaTeX note (required symbols): “Gets” is \( \gt \) “has” for expressing the action of acquiring.