The following passage is from a science article about Mars. Which punctuation mark should be placed in the blank to ensure the sentence conforms to the conventions of Standard English?
Cevap:In their ongoing study of ancient Martian topography, planetary scientists have noted that the planet's rugged southern highlands【—】a heavily cratered, ancient region that preserves the crustal signatures of the early solar system—stand in stark contrast to the smooth, low-lying volcanic plains of the northern hemisphere, which were resurfaced by lava flows billions of years ago.
Cevap
A dash (or em dash)
The sentence contains a nonessential parenthetical appositive phrase ('a heavily cratered, ancient region that preserves the crustal signatures of the early solar system') that interrupts the main clause between the subject ('highlands') and the verb ('stand'). Standard English conventions require that nonessential elements be set off with matching punctuation: either two commas, two parentheses, or two dashes. Because the closing punctuation of this phrase is an em dash ('system—stand'), the opening punctuation at the blank must also be a matching em dash.
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Anahtar Kavram
Parenthetical Punctuation and Dash Alignment