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Soru

Zorluk: ZorColons, Semicolons, and Dashes

Biologists studying the migrations of the monarch butterfly (*Danaus plexippus*) have long marveled at the insect's navigation systems. These systems—which rely on a 'time-compensated sun compass' that integrates visual cues with circadian rhythms_______ enable the butterflies to travel thousands of miles to their overwintering sites in Mexico.

Which choice completes the text so that it conforms to the conventions of Standard English?

  1. A
    rhythms,
  2. rhythms—Cevap
  3. C
    rhythms;
  4. D
    rhythms

Cevap

rhythms—
The phrase 'which rely on a "time-compensated sun compass" that integrates visual cues with circadian rhythms' functions as a nonessential clause modifying the subject 'systems'. Standard English conventions dictate that nonessential information must be enclosed by matching punctuation marks. Because the clause is introduced by an em-dash after 'systems', it must be closed with a matching em-dash before the main verb 'enable'. The choice ending with an em-dash correctly maintains this punctuation symmetry.

Adım Adım Çözüm

1
Analyze the sentence structure to locate the main subject and verb, and identify any intervening clauses.
The main subject is 'systems' and the main verb is 'enable'. The clause starting with 'which' is a nonessential clause modifying 'systems'.
Identifying the clause boundaries helps determine how it should be punctuated relative to the rest of the sentence.
2
Identify the punctuation mark that opens the nonessential clause.
The clause is opened with an em-dash after the word 'systems'.
Nonessential elements must be set off by matching punctuation marks on both sides (either two commas, two parenthetical curves, or two em-dashes).
3
Select the option that matches the opening punctuation mark and properly closes the nonessential clause before the verb 'enable'.
The option containing a closing em-dash ('rhythms—') successfully completes the punctuation pair.
Using any other punctuation mark or no punctuation mark at all would cause an asymmetry or grammatical error.

Anahtar Kavram

Punctuation of nonessential elements with matching punctuation marks (specifically em-dashes).
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Konular

Colons, Semicolons, and Dashes

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