Based on the passage about the Alaska pipeline, choose the option that correctly explains what "bents" are in the context of the pipeline structure.

Introduction / Context:
This question tests your ability to recall a specific technical term introduced in the passage about the Alaska pipeline. The word "bents" may be unfamiliar, but the passage clearly defines it in context. The exam assesses whether you noticed and understood that definition while reading.

Given Data / Assumptions:

• The passage describes sections of the pipeline that are elevated above ground.
• It mentions that these sections rest on structures called "bents".
• The text explains what these "bents" look like and what they are made of.
• The options offer different interpretations of the term "bents".

Concept / Approach:
When a passage introduces a specialised term, it often defines it immediately. Here, the passage uses the phrase "Resting on H shaped steel racks called 'bents'". This means that "bents" are the H shaped racks themselves, not the route or sections of pipe. Our job is simply to match this explanation with the correct option.

Step-by-Step Solution:
Step 1: Recall the specific line from the passage: "Resting on H shaped steel racks called 'bents', long sections of the pipeline follow a zigzag course high above the frozen earth."Step 2: Identify the definition embedded in that line. The racks are "H shaped", "steel", and are referred to as "bents".Step 3: Notice that the zigzag course is the route of the pipeline, not the definition of "bents".Step 4: Compare with the options. Option D, "The H shaped steel racks", directly reproduces the definition given in the passage.Step 5: Option A, "Zigzag shape of pipeline", refers to the pattern of the pipeline's course, not the supporting structure.Step 6: Option B, "Pipeline's up and down route", again describes the overall pattern of elevation and burial, not "bents".Step 7: Option C, "The section of the pipeline that drops out of sight", describes a different feature mentioned in the passage where pipes go underground, not the supports.Step 8: Therefore, option D is the correct interpretation.

Verification / Alternative check:
We can paraphrase the relevant sentence: the pipeline sections that are above ground do so because they rest on supports, which are H shaped frames made of steel, and these supports are called "bents". The passage later describes other sections that drop below ground and rise again, showing that "bents" are limited to elevated segments. This confirms that "bents" correspond specifically to the H shaped supporting racks, not the route or buried parts of the pipeline.

Why Other Options Are Wrong:
Option A incorrectly treats "bents" as the pipeline's zigzag shape, but the passage clearly distinguishes the supports from the path they enable.
Option B confuses the structural supports with the overall up and down pattern of the pipeline, which is determined by climate and terrain but is not itself called "bents".
Option C mistakes underground sections of pipe for "bents", even though the text clearly associates "bents" with sections that are elevated above the ground, not buried.

Common Pitfalls:
Some readers skim over technical terms, not realising that the passage immediately defines them. Others may not clearly separate the support structures from the pipeline route when recalling the description. To avoid such mistakes, train yourself to pause whenever you see a term in quotation marks or followed by a descriptive clause, as that usually signals an important definition for later questions.

Final Answer:
In the passage, "bents" are the H shaped steel racks that support elevated sections of the pipeline, so the correct option is D.