This sentence does not contain commas where necessary. The phrase "which ususally occurred via email" is an example of a relative clause, which gives more information about its antecedent: conversations. Any such phrase that occurs in the middle of a sentence must be introduced and completed with a comma. The correct choice is, "In their conversations, which usually occurred via email, Monica and Jess."

This sentence does not contain punctuation where it is necessary. The phrase "While cement and steel are already strong materials" is an example of an introductory phrase, explaining information necessary to the context of the sentence, but outside of the main sentence, grammatically. These types of phrases must be followed by a comma in order to separate them from the rest of the sentence. The correct answer choice is, "cement and steel are already strong materials, they are especially strong."

This sentence misuses a comma. The phrase "due to the industrial revolution and the increase of opportunities" is just that - one phrase. All of these words are part of one clause, so there is no reason for a comma before the word "and." Commas only appear before conjunctions when the conjunction is used to combine two independent clauses. The best choice is, "due to the industrial revolution and the increase of opportunities in cities." 

This sentence misuses a comma. Commas only appear before conjunctions when the conjunction is used to combine two independent clauses. The words on both sides of "and," however, are part of the same clause. No additional punctuation is necessary. The correct choice is, "because of his low fees and amazing customer service."

This sentence misuses a comma. There is no need for a comma before the word "that" since it is not separating one clause from another, combining clauses with a conjunction, separating items in a list, or any other reason for which a comma should be used. The correct choice is to omit the comma as in the option: "Many individuals believe that driverless cars will fill our roads."

This sentence misuses a comma. The sentence combines two related independent clauses without the use of a coordinate conjunction; when this is the case, a semicolon should be placed between those clauses. A semicolon should come after the word "lifespan."

The phrase "for many computers" is an example of an introductory phrase, explaining information necessary to the context of the sentence, but outside of the main sentence, grammatically. These types of phrases must be followed by a comma in order to separate them from the rest of the sentence. 

While one choice uses a period, which could be correct, the following word, "for," is not capitalized, so it cannot be correct. The correct choice is, "Computers have a short lifespan; for many computers,"

The phrase "which were essential for the company's records" is an example of a relative clause, which gives more information about its antecedent: the documents. Any such phrase that occurs in the middle of a sentence must be introduced and completed with a comma. You would not use hyphens to separate these clauses; usually, hyphens are more common between clauses when adding an interjection. The correct answer choice, which corrects the error without changing the meaning of the sentence, is "the documents, which were essential for the company's records, meant Fatima would." 

This sentence does not contain a comma where one is necessary. The phrase "a well known composer" is an example of a parenthetical expression: a phrase that explains more about a particular word or phrase in the sentence, but is not introduced by a relative pronoun. These phrases must be introduced and completed with a comma in order to separate them from the main clause of the sentence. The correct answer choice is, "Bach, a well known composer, wrote many."

This sentence misuses a comma. The phrase "Because of farming and herding" is an introductory phrase, explaining information necessary to the context of the sentence, but outside of the main sentence, grammatically. These types of phrases must be followed by a comma in order to separate them from the rest of the sentence. A comma is not necessary, however, before the "and," because the phrase "farming and herding" is not a list (a list contains three or more items), and it is not combining independent clauses. The correct choice is, "Because of farming and herding, humans are able."

This sentence does not contain commas where necessary. The phrase "one of the top schools in the United States" is an example of a relative clause, which gives more information about its antecedent: Harvard. Any such phrase that occurs in the middle of a sentence must be introduced and completed with a comma. The correct choice is, "Harvard, one of the top schools in the United States, has an endowment worth billions of dollars."