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Sentence Correction: Tenses - Past Simple and Progressive

Prior to the professionalization of medical practice in modern times, surgical procedures and dentistry were performed by barbers, who were experts at cutting hair, extracting teeth, and letting blood.

Incorrect.

This answer choice makes an unnecessary change to the original sentence and is stylistically flawed.

The phrase extractors of teeth is awkward and redundant.

Expert as is non-idiomatic in English.

Well done!

This answer choice makes correct use of parallelism. The three items in the list are non-conjugated verbs of the same form cutting, extracting, letting.

Incorrect.

This answer choice is grammatically incorrect

By changing the tense to Past Progressive, the corrected sentence describes actions that were in progress at some time in the past. However, the original sentence describes a general historical fact that was true in the past. The correct tense for expressing this is Past Simple, which is also logically parallel with the tense of the first conjugated verb in the sentence were performed

Incorrect.

This answer choice is illogical and changes the meaning of the original sentence.

The parallel construction experts at cutting hair or barbers is illogical: the two items are not alternatives. Rather, barbers are experts at cutting hair.

Also, this answer choice makes it seem as if experts either cut hair or they cut barbers!

Incorrect.

This answer choice is illogical and changes the meaning of the original sentence.

By replacing the non-defining relative pronoun who with the defining pronoun that, the corrected sentence changes the meaning of the original sentence. The original sentence claims that in the past barbers used to perform surgery, and adds additional general information about barbers in the relative clause (following who).

The corrected sentence, however, claims that surgery was performed only by barbers who were experts at all three skills: cutting hair, extracting teeth, and letting blood. The use of the adverb expertly reinforces this meaning. This is illogical as it doesn't allow for the possibility that some barbers may have been incompetent.

barbers, who were experts at cutting hair, extracting teeth, and letting blood. 
barbers, who were experts as hair-cutters, extractors of teeth and blood-letters.
barbers, who were expertly cutting hair, extracting teeth, and letting blood.
experts at cutting hair or barbers, who could extract teeth and also let blood.
barbers that cut hair, extracted teeth, and let blood expertly.