Punctuation Exercise #1 (Commas)

Punctuation Exercise #1 (Commas)

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In the following sentences, click on the places where the comma is undesired, is missing, or should be changed to another piece of punctuation. Note that each sentence has at most one punctuation error. If no error exists, click on "No error." Corresponding information for this exercise can be found in The Craft of Editing (denoted CE) and The Craft of Scientific Writing (denoted CSW). Note: In the general preferences of your browser, please do not underline links and do not override this document's choice of font colors.

The new material, which will be available next week is composed of plastic and iodine.
(No error)

#1. Congratulations, you have found an error.
Revision: The new material, which will be available next week, is composed of plastic and iodine.
Discussion: missing parenthetical comma for "which" clause.

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As World War II escalated the United States became locked into a race with Germany to develop the first atomic bomb.
(No error)

#2. Congratulations, you have found an error.
Revision: As World War II escalated, the United States became locked into a race with Germany to develop the first atomic bomb.
Discussion: missing comma following introductory clause. Note that without the comma, the reader does not know where the introductory clause ends.

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The three largest earthquakes occurred in San Francisco, Tokyo, and Lima.
(No error)

#3. Congratulations, you have answered correctly.
Original: The three largest earthquakes occurred in San Francisco, Tokyo, and Lima.
Discussion: While the comma following "Tokyo" is optional, it is certainly not incorrect.

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On February 5, 1990 Mount St. Helens had another eruption, this one smaller than the eruption 10 years before.
(No error)

#4. Congratulations, you have found an error.
Revision: On February 5, 1990, Mount St. Helens had another eruption, this one smaller than the eruption 10 years before.
Discussion: missing parenthetical comma. The year "1990" is parenthetical information about the date February 5. Although some publications treat this comma as optional, many more (including the Wall Street Journal and the New York Times) do not. Note that if the date had been written as "5 February 1990," then a simple comma following "1990" would have been appropriate. Also note that the comma following "eruption" is correct because what follows is a phrase.

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Every year, an earthquake of magnitude between 8.0 and 8.9 on the Richter scale, will be experienced somewhere in the world [Haughton, 1989].
(No error)

#5. Congratulations, you have found an error.
Revision: Every year, an earthquake of magnitude between 8.0 and 8.9 on the Richter scale will be experienced somewhere in the world [Haughton, 1989].
Discussion: undesired comma. Note that while the comma following "year" is optional, it is certainly not incorrect. Also note that the punctuation for the reference listing at the end of the sentence depends upon the format.

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As the flame front propagates hot combustion products expand, resulting in a rapid pressure increase.
(No error)

#6. Congratulations, you have found an error.
Revision: As the flame front propagates, hot combustion products expand, resulting in a rapid pressure increase.
Discussion: missing comma following the introductory clause. Without the comma, the audience does not know when the clause ends.

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The concentrations of these gases, which are called greenhouse gases control how much infrared radiation escapes.
(No error)

#7. Congratulations, you have found an error.
Revision: The concentrations of these gases, which are called greenhouse gases, control how much infrared radiation escapes.
Discussion: missing parenthetical comma for the "which" clause.

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After 1987 parachuting accidents decreased significantly because instructors started teaching novices with tandem jumps rather than static lines.
(No error)

#8. Congratulations, you have found an error.
Revision: After 1987, parachuting accidents decreased significantly because instructors started teaching novices with tandem jumps rather than static lines.
Discussion: missing comma following the introductory phrase. Without the comma, the audience trips.

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On May 18, 1980, a cloud of hot rock and gas surged northward from Mount St. Helens.
(No error)

#9. Congratulations, you have answered correctly.
Revision: On May 18, 1980, a cloud of hot rock and gas surged northward from Mount St. Helens.
Revision: This sentence is punctuated correctly.

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The synergistic reactor contains a chamber in which the exhaust from the burning coal mixes with limestone, see Appendix A.
(No error)

#10. Congratulations, you have found an error.
Revision: The synergistic reactor contains a chamber in which the exhaust from the burning coal mixes with limestone, as discussed in Appendix A.
Discussion: The original is a run-on. One solution (given here) is to make the reference to Appendix A a verb phrase. Another solution is to create a separate sentence. Still a third is to use parentheses to refer to Appendix A.

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The local economy should benefit from the operation. Local property taxes would decrease for area residents and the Nicolet Minerals Company, formerly the Crandon Mining Company, is expected to spend more than $40 million on local goods and services.
(No error)

#11. Congratulations, you have found an error.
Revision: The local economy should benefit from the operation. Local property taxes would decrease for area residents, and the Nicolet Minerals Company, formerly the Crandon Mining Company, is expected to spend more than $40 million on local goods and services.
Discussion: Without the comma before "and," the audience doesn't know where the first independent clause ends and the second one begins.

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Last updated 2/99
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