Question

Difficulty: EasyPunctuation of Nonessential Elements

Located in the asteroid belt between Mars and Jupiter, the dwarf planet Ceres is the largest object in that region. Ceres _______ contains a significant amount of water ice beneath its rocky crust. This discovery has led scientists to study the celestial body for clues about the early solar system.

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

  1. , which was discovered by Giuseppe Piazzi in 1801,Answer
  2. B
    , which was discovered by Giuseppe Piazzi in 1801
  3. C
    —which was discovered by Giuseppe Piazzi in 1801,
  4. D
    which was discovered by Giuseppe Piazzi in 1801,

Answer

The correct option is the one that sets off the nonessential relative clause with a matching pair of commas: ', which was discovered by Giuseppe Piazzi in 1801,'
The clause 'which was discovered by Giuseppe Piazzi in 1801' is nonessential to the main meaning of the sentence. In Standard English, nonessential elements must be set off with matching punctuation marks on both sides. The option that begins with a comma and ends with a comma correctly and symmetrically sets off this clause.

Step-by-Step Solution

1
Identify the nonessential element in the sentence.
The clause 'which was discovered by Giuseppe Piazzi in 1801' is a nonessential relative clause because it provides extra information about Ceres that is not essential to the main grammatical structure of the sentence.
Nonessential elements must be set off from the rest of the sentence by matching punctuation marks.
2
Select the option that uses a matching pair of punctuation marks to isolate this clause.
The option starting and ending with a comma correctly isolates the nonessential clause.
Using mismatched punctuation (such as an em dash and a comma) or omitting one of the boundary punctuation marks creates grammatical asymmetry.

Key Concept

Punctuation of Nonessential Elements
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