The following sentence is missing punctuation: “The crowd upset by the delay began to chant loudly for the band to appear.” Explain where the error has occurred in this sentence and how it can be fixed.

Read the sentence aloud. Where do you naturally pause? Two commas are needed in this sentence to represent those pauses and help comprehension.

http://grammar.ccc.commnet.edu/grammar/commas.htm

See #4.

The error in this sentence is the lack of a punctuation mark to separate the introductory phrase from the main clause. The introductory phrase is "The crowd upset by the delay," which provides additional information about the subject of the sentence. To fix this error, a comma should be placed after the introductory phrase. The corrected sentence would be: "The crowd, upset by the delay, began to chant loudly for the band to appear."