The phrase "preferring to use simplifying language" is a dependent clause, a clause that cannot be used as a complete sentence but instead relies on other information. Although it cannot stand alone, it still needs to be separated from the rest of the sentence by a comma; therefore, the correct answer is " displays of his verbal acuity, preferring to use simplified language."

The only problem with the sentence is that it is a compound sentence, shoved into a run on sentence. The sentence consists of two complete thoughts, joined by the conjunction "which." All such sentences must be divided by a comma before the conjunction, making "than the youngest kid, which allowed him" the correct answer choice.

A comma is not needed between independent and dependent clauses when the independent clause comes first: "The President initially vetoed the bill in order . . ."

The phrase "with the only exception being Fridays" is a dependent clause, and needs to be clearly distinguished from the main clause of the sentence. The best way to do this is by setting a comma between the two parts. The only answer choice that correctly places a comma in the sentence is "He typically worked late, with the only exception being Fridays."

The phrase "despite having none to conduct" is a dependent clause, a clause that cannot stand as a complete sentence on its own, but provides extra explanation to the body of the sentence. A dependent clause always needs to be set apart from the rest of the sentence by a comma. The only answer choice that does this is "The former bandleader still dreamed about conducting an ensemble despite having none to conduct."

The phrase "which stressed their underlings" is a dependent clause, or a clause that relies on the main body of the sentence for its full meaning. Any dependent clause must be set apart from the main body of the sentence by a comma. The answer choice that appropriately uses such a comma is "The managers decided to make a change for no particular reason, which stressed their underlings."

The phrase underlined at the end of the sentence is one whole and complete phrase. Thus, the use of a comma anywhere in the phrase is grammatically incorrect. "Speculation by scholars" is the correct answer choice.

Since "but she wasn't sure she would be able to write a novel" is a dependent clause (composed of a conjunction, a subject, and a verb), there needs to be a comma before the conjunction "but" in order to seperate it from the independent clause.

The underlined portion of the sentence contains a small punctuation problem. Specifically, the phrase "as the pain was too much to bear," is a phrase that explains the sentence, but is not necessary to its construction. All such phrases need a comma to separate them from the body of the sentence. "Rarely talked to his children as the pain was too much for him to bear," is the best answer choice.

A dependent clause, or a clause which cannot stand on its own, must be separated from the main clause in a sentence by a comma. The full dependent clause in the example sentence is the introductory phrase "When you talk to your mother like that," not "when you talk to your mother like." Thus, the comma attempting to separate the introductory clause in the sentence above actually creates a comma splice error. The best way to correct the underlined portion above is, "When you talk to your mother like that, you bring shame on the whole family."