Examkin

Question

Difficulty: MediumPunctuation of Nonessential Elements

The following passage is from a biology text. Which punctuation mark must be inserted into the blank to ensure the sentence conforms to the conventions of Standard English?

Answer:First discovered in 1998 off the coast of Sulawesi, the mimic octopus—a highly intelligent cephalopod capable of dynamic mimicry【—】is able to impersonate toxic species such as lionfish and sea snakes to deter predators.

Answer

An em dash (—) is required to correctly close the nonessential element.
The sentence contains a nonessential appositive phrase ('a highly intelligent cephalopod capable of dynamic mimicry') that interrupts the flow between the subject ('the mimic octopus') and the verb ('is able'). Because this nonessential element is introduced with an em dash, it must also close with an em dash to maintain punctuation symmetry.

Step-by-Step Solution

1
Identify the nonessential element in the sentence.
The phrase 'a highly intelligent cephalopod capable of dynamic mimicry' is a nonessential appositive phrase modifying 'the mimic octopus'.
This phrase can be removed without changing the core grammatical structure of the sentence.
2
Examine the punctuation introducing the nonessential element.
An em dash ('—') is used immediately before the phrase.
Nonessential elements must be set off by matching pairs of punctuation marks: two commas, two em dashes, or a pair of parentheses.
3
Determine the punctuation mark needed to close the nonessential element.
An em dash ('—') must be placed in the blank.
Using any other punctuation mark would cause punctuation asymmetry, which violates Standard English conventions.

Key Concept

Punctuation of Nonessential Elements
Rate this question

Topics

Punctuation of Nonessential Elements

More questions from this topic