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Zorluk: OrtaParaphrased Fact Recognition

In heavy-duty diesel engines equipped with Selective Catalytic Reduction (SCR) systems, Diesel Exhaust Fluid (DEF)—a high-purity aqueous urea solution—is injected into the hot exhaust stream upstream of the catalytic converter. At temperatures exceeding 200°C, the injected urea decomposes into ammonia and isocyanic acid. When these chemical vapors enter the SCR catalyst, the ammonia reacts with harmful nitrogen oxides (NOxNO_x) to produce harmless nitrogen gas and water vapor. Maintaining adequate exhaust thermal energy is essential, as temperatures below the reaction threshold lead to incomplete decomposition, resulting in solid urea deposits that restrict exhaust flow and decrease emissions reduction efficiency.

According to the passage, what occurs when the exhaust system fails to maintain sufficient heat?

  1. A
    The catalytic converter automatically shuts down to prevent physical damage from chemical vapors.
  2. Solid residues accumulate and obstruct the pathway of exhaust gases.Cevap
  3. C
    The injected urea decomposes into ammonia and isocyanic acid inside the catalytic converter.
  4. D
    Exhaust temperatures fall below 200°C because nitrogen oxides convert into water vapor.

Cevap

Solid residues accumulate and obstruct the pathway of exhaust gases.
The passage explicitly states that when temperatures drop below the required operating threshold, incomplete chemical breakdown causes solid urea deposits that restrict exhaust flow. The correct option accurately conveys this exact cause-and-effect relationship by stating that solid residues build up and block exhaust pathways without relying on copied verbatim phrasing.

Adım Adım Çözüm

1
Identify the key condition targeted by the question stem.
The question asks for the consequence of failing to maintain sufficient exhaust heat (temperatures below the reaction threshold).
Locating the exact condition in the text ensures accurate factual retrieval.
2
Locate the relevant sentence in the paragraph discussing low temperature consequences.
The passage states that temperatures below the threshold lead to 'incomplete decomposition, resulting in solid urea deposits that restrict exhaust flow and decrease emissions reduction efficiency.'
This establishes the exact factual details provided by the author.
3
Match the factual finding to the choice using synonymous phrasing and restructured syntax.
'Solid urea deposits that restrict exhaust flow' corresponds directly to 'Solid residues accumulate and obstruct the pathway of exhaust gases.'
Paraphrased fact recognition requires identifying identical meaning expressed through alternative vocabulary and sentence structure.

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Paraphrased Fact Recognition
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Paraphrased Fact Recognition

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