Extract:
Which word is used incorrectly in the following sentence?
Jack practices piano while Sidney study for the exam.
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A
practices
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B
while
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C
study
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D
exam
The word "study" is used incorrectly; the singular subject "Sidney" requires third-person singular verb form "studies."
A) practices
"Practices" correctly uses third-person singular -s ending matching singular subject "Jack." No error affects this verb form.
B) while
"While" is correctly used as a subordinating conjunction linking simultaneous actions. No error affects this conjunction.
C) study
"Study" lacks required third-person singular -s ending for present tense verb with singular subject "Sidney." Standard subject-verb agreement requires "Sidney studies" not "Sidney study."
D) exam
"Exam" is correctly used as singular noun object. No error affects this noun.
Conclusion
Present tense verbs with third-person singular subjects (he/she/it/names) require -s/-es endings. "Sidney" as singular proper noun demands "studies", not base form "study", to maintain subject-verb agreement in present tense constructions.