Question

This question has five answer choices, labeled A through E. Select and indicate the best answer from among these choices.
The passage is primarily concerned with

• A. refuting a hypothesis advanced by scientists
• B. discussing the importance of a phenomenon
• C. presenting a possible explanation of a phenomenon
• D. contrasting two schools of thought
• E. discussing the origins of a theory
• A. The pull theory is not universally accepted by scientists.
• B. The pull theory depends on one of water's physical properties.
• C. The pull theory originated earlier than did the push theory.
• A. when the pull theory originated
• B. the amount of water a tall tree can transport
• C. the significance of water's tensile strength in the pull theory
• D. the role of the sun in the pull theory
• M. the mechanism underlying water's tensile strength

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
This is a primary purpose question, asking for the main idea of the passage. We need to analyze the overall structure and content to determine what the author is trying to achieve.
Step 2: Detailed Explanation:
The passage begins by describing a phenomenon: how a tall tree transports hundreds of gallons of water. It then poses a question: is it a push or pull mechanism? The rest of the passage is dedicated to explaining the favored theory—the "pull mechanism." It describes how this theory works, what property it relies on (tensile strength), and its energy source (the sun). The passage's main goal is to explain this scientific theory.
Analyzing the Options:
(A) refuting a hypothesis advanced by scientists: The author does not refute the pull theory; they explain and support it as the "favored" one.
(B) discussing the importance of a phenomenon: The passage explains \textit{how} water transport works, not \textit{why} it is important to the tree or ecosystem.
(C) presenting a possible explanation of a phenomenon: This accurately describes the passage. The phenomenon is water transport in trees, and the passage presents the "pull mechanism" as the leading explanation.
(D) contrasting two schools of thought: While the passage briefly mentions "pushing from below," it spends almost the entire time explaining the "pull" theory. It does not give equal weight to two schools of thought or contrast them in detail.
(E) discussing the origins of a theory: The passage mentions the theory was "first proposed in the late 1800's," but this is a minor detail. The primary focus is on explaining how the theory works, not on its historical development.
Step 3: Final Answer:
The main focus of the passage is to lay out the details of the "pull" theory as an explanation for the phenomenon of water transport in trees.

Answer 2

Step 1: Understanding the Concept:
This is a "select all that apply" question that requires us to verify each statement against the information given in the passage. We must find direct or strongly implied support for each correct statement.
Step 2: Detailed Explanation:
Analyzing the Options:
(A) The pull theory is not universally accepted by scientists.
The passage states that the pull mechanism "has long been favored by most scientists." The word "most" implies that some scientists do not favor it, meaning it is not universally accepted. This statement is supported by the passage.
(B) The pull theory depends on one of water's physical properties.
The passage explicitly states that the theory "relies on a property of water not commonly associated with fluids: its tensile strength." Tensile strength is a physical property. This statement is directly supported by the passage.
(C) The pull theory originated earlier than did the push theory.
The passage introduces the push vs. pull question at the beginning but gives no historical information about the "push" theory. It only states that the pull theory was "first proposed in the late 1800's." We cannot compare their origins based on the text. This statement is not supported by the passage.
Step 3: Final Answer:
Based on the text, statements (A) and (B) are both supported.

Answer 3

Step 1: Understanding the Concept:
This is an "EXCEPT" question. We must find which of the five topics is NOT discussed in the passage. The correct answer will be the one for which no information is provided. We can use a process of elimination by finding the information for the other four options.
Step 2: Detailed Explanation:
Let's locate the information for each option in the passage:
(A) when the pull theory originated: The passage states, "First proposed in the late 1800's...". This information is provided.
(B) the amount of water a tall tree can transport: The first sentence says, "A tall tree can transport a hundred gallons of water a day...". This information is provided.
(C) the significance of water's tensile strength in the pull theory: The passage says the theory "relies on a property of water... its tensile strength." and explains how this property allows water to be tugged down from the treetop. Its significance is clearly explained. This information is provided.
(D) the role of the sun in the pull theory: The last sentence says, "...all the energy for lifting water comes from the sun's evaporative power." This information is provided.
(E) the mechanism underlying water's tensile strength: The passage states that the theory relies on tensile strength, but it never explains \textit{what causes} this property in water. It does not mention cohesion, adhesion, or hydrogen bonds, which are the underlying mechanisms. This information is NOT provided in the passage.
Step 3: Final Answer:
The passage mentions and uses the concept of tensile strength, but it does not explain the physical mechanism that causes it. Therefore, (E) is the correct answer.