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Question

Difficulty: HardSelecting Concluding Sentences and Transitions

Art conservators restoring Renaissance frescoes have historically relied on chemical solvents and physical scraping, both of which risk stripping away delicate pigments. Recently, however, laser ablation has emerged as a revolutionary tool in art conservation. By emitting brief pulses of light at precise wavelengths, lasers can vaporize layers of soot and dirt without heating the underlying paint. Because different materials absorb light at distinct rates, the laser can be calibrated to target only the dark grime while reflecting harmlessly off the lighter mineral pigments of the fresco.

Therefore, this absorption process is self-limiting, it prevents accidental over-cleaning. Once the dark soot is removed, the laser no longer has any effect on the surface. Ultimately, this synthesis of physics and art history ensures that these fragile masterpieces are preserved with unprecedented accuracy, allowing them to endure for future generations.

Which choice provides the most logical and effective transition from the preceding paragraph?

  1. A
    NO CHANGE
  2. B
    In contrast, this chemical reaction is self-limiting.
  3. Consequently, this optical selectivity makes the cleaning process self-limiting.Answer
  4. D
    On the other hand, the laser's safety is self-limiting, and it will have prevented future damage.

Answer

The option starting with 'Consequently, this optical selectivity' is the correct answer because it uses the correct causal transition to connect the paragraphs and maintains proper grammar and tense consistency.
The correct option correctly uses the transition word 'consequently' to signal a cause-and-effect relationship between the first paragraph (which details how different materials absorb light at different rates) and the second paragraph (which explains that the cleaning process is self-limiting). It also avoids any grammatical errors and maintains a consistent present tense.

Step-by-Step Solution

1
Analyze the relationship between the two paragraphs.
The first paragraph explains the physics of how the laser is calibrated to target only grime. The second paragraph describes how the process naturally stops when the grime is gone. This is a cause-and-effect relationship, meaning a causal transition like 'consequently' or 'therefore' is required.
Understanding the logical connection between the paragraphs helps narrow down the appropriate transition words.
2
Evaluate the grammar of the options that use causal transitions.
The original text (NO CHANGE) uses 'Therefore' but contains a comma splice by joining two independent clauses with just a comma. The correct option uses 'Consequently' and is grammatically correct as a single independent clause.
Eliminating grammatically incorrect choices is essential, as ACT questions test both logical transitions and standard English conventions.
3
Evaluate the remaining options for logic, factuality, and tense consistency.
The options using 'in contrast' and 'on the other hand' are incorrect because they suggest opposition. Additionally, one of them introduces a factual error ('chemical reaction') and another introduces an unnecessary shift in verb tense ('will have prevented').
Verifying that the correct choice maintains factual consistency with the passage and consistent tense ensures the best stylistic fit.

Key Concept

Selecting logical paragraph transitions that maintain grammatical correctness and tense consistency.
Estimated Time:1m 30s
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Topics

Selecting Concluding Sentences and Transitions

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